/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      https://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.lang3.exception;
  
  import java.io.PrintStream;
  import java.io.PrintWriter;
  import java.io.StringWriter;
  import java.lang.reflect.Method;
  import java.lang.reflect.UndeclaredThrowableException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.Objects;
  import java.util.StringTokenizer;
  import java.util.function.Consumer;
  import java.util.stream.Stream;
  
  import org.apache.commons.lang3.ArrayUtils;
  import org.apache.commons.lang3.ClassUtils;
  import org.apache.commons.lang3.StringUtils;
  import org.apache.commons.lang3.reflect.MethodUtils;
  import org.apache.commons.lang3.util.IterableStringTokenizer;
  
  /**
   * Provides utilities for manipulating and examining
   * {@link Throwable} objects.
   *
   * @since 1.0
   */
  public class ExceptionUtils {
  
      /**
       * The names of methods commonly used to access a wrapped exception.
       */
      // TODO: Remove in Lang 4
      private static final String[] CAUSE_METHOD_NAMES = {
          "getCause",
          "getNextException",
          "getTargetException",
          "getException",
          "getSourceException",
          "getRootCause",
          "getCausedByException",
          "getNested",
          "getLinkedException",
          "getNestedException",
          "getLinkedCause",
          "getThrowable",
      };
  
      private static final int NOT_FOUND = -1;
  
      /**
       * Used when printing stack frames to denote the start of a
       * wrapped exception.
       *
       * <p>Package private for accessibility by test suite.</p>
       */
      static final String WRAPPED_MARKER = " [wrapped] ";
  
      /**
       * Throws the given (usually checked) exception without adding the exception to the throws
       * clause of the calling method. This method prevents throws clause
       * inflation and reduces the clutter of "Caused by" exceptions in the
       * stack trace.
       * <p>
       * The use of this technique may be controversial, but useful.
       * </p>
       * <pre>
       *  // There is no throws clause in the method signature.
       *  public int propagateExample {
       *      try {
       *          // Throws IOException
       *          invocation();
       *      } catch (Exception e) {
       *          // Propagates a checked exception.
       *          throw ExceptionUtils.asRuntimeException(e);
       *      }
       *      // more processing
       *      ...
       *      return value;
       *  }
       * </pre>
       * <p>
       * This is an alternative to the more conservative approach of wrapping the
      * checked exception in a RuntimeException:
      * </p>
      * <pre>
      *  // There is no throws clause in the method signature.
      *  public int wrapExample() {
      *      try {
      *          // throws IOException.
      *          invocation();
      *      } catch (Error e) {
      *          throw e;
      *      } catch (RuntimeException e) {
      *          // Throws an unchecked exception.
      *          throw e;
      *      } catch (Exception e) {
      *          // Wraps a checked exception.
      *          throw new UndeclaredThrowableException(e);
      *      }
      *      // more processing
      *      ...
      *      return value;
      *  }
      * </pre>
      * <p>
      * One downside to using this approach is that the Java compiler will not
      * allow invoking code to specify a checked exception in a catch clause
      * unless there is some code path within the try block that has invoked a
      * method declared with that checked exception. If the invoking site wishes
      * to catch the shaded checked exception, it must either invoke the shaded
      * code through a method re-declaring the desired checked exception, or
      * catch Exception and use the {@code instanceof} operator. Either of these
      * techniques are required when interacting with non-Java JVM code such as
      * Jython, Scala, or Groovy, since these languages do not consider any
      * exceptions as checked.
      * </p>
      *
      * @param throwable
      *            The throwable to rethrow.
      * @param <T> The type of the returned value.
      * @return Never actually returned, this generic type matches any type
      *         which the calling site requires. "Returning" the results of this
      *         method, as done in the propagateExample above, will satisfy the
      *         Java compiler requirement that all code paths return a value.
      * @since 3.14.0
      * @see #wrapAndThrow(Throwable)
      */
     public static <T extends RuntimeException> T asRuntimeException(final Throwable throwable) {
         // claim that the typeErasure invocation throws a RuntimeException
         return ExceptionUtils.<T, RuntimeException>eraseType(throwable);
     }
 
     /**
      * Claims a Throwable is another Throwable type using type erasure. This
      * hides a checked exception from the Java compiler, allowing a checked
      * exception to be thrown without having the exception in the method's throw
      * clause.
      */
     @SuppressWarnings("unchecked")
     private static <R, T extends Throwable> R eraseType(final Throwable throwable) throws T {
         throw (T) throwable;
     }
 
     /**
      * Performs an action for each Throwable causes of the given Throwable.
      * <p>
      * A throwable without cause will return a stream containing one element - the input throwable. A throwable with one cause
      * will return a stream containing two elements. - the input throwable and the cause throwable. A {@code null} throwable
      * will return a stream of count zero.
      * </p>
      *
      * <p>
      * This method handles recursive cause structures that might otherwise cause infinite loops. The cause chain is
      * processed until the end is reached, or until the next item in the chain is already in the result set.
      * </p>
      *
      * @param throwable The Throwable to traverse.
      * @param consumer a non-interfering action to perform on the elements.
      * @since 3.13.0
      */
     public static void forEach(final Throwable throwable, final Consumer<Throwable> consumer) {
         stream(throwable).forEach(consumer);
     }
 
     /**
      * Introspects the {@link Throwable} to obtain the cause.
      *
      * <p>
      * The method searches for methods with specific names that return a {@link Throwable} object. This will pick up most wrapping exceptions, including those
      * from JDK 1.4.
      * </p>
      *
      * <p>
      * The default list searched for are:
      * </p>
      * <ul>
      * <li>{@code getCause()}</li>
      * <li>{@code getNextException()}</li>
      * <li>{@code getTargetException()}</li>
      * <li>{@code getException()}</li>
      * <li>{@code getSourceException()}</li>
      * <li>{@code getRootCause()}</li>
      * <li>{@code getCausedByException()}</li>
      * <li>{@code getNested()}</li>
      * </ul>
      *
      * <p>
      * If none of the above is found, returns {@code null}.
      * </p>
      *
      * @param throwable the throwable to introspect for a cause, may be null.
      * @return the cause of the {@link Throwable}, {@code null} if none found or null throwable input.
      * @since 1.0
      * @deprecated This feature will be removed in Lang 4, use {@link Throwable#getCause} instead.
      */
     @Deprecated
     public static Throwable getCause(final Throwable throwable) {
         return getCause(throwable, null);
     }
 
     /**
      * Introspects the {@link Throwable} to obtain the cause.
      *
      * <p>
      * A {@code null} set of method names means use the default set. A {@code null} in the set of method names will be ignored.
      * </p>
      *
      * @param throwable   the throwable to introspect for a cause, may be null.
      * @param methodNames the method names, null treated as default set.
      * @return the cause of the {@link Throwable}, {@code null} if none found or null throwable input.
      * @since 1.0
      * @deprecated This feature will be removed in Lang 4, use {@link Throwable#getCause} instead.
      */
     @Deprecated
     public static Throwable getCause(final Throwable throwable, String[] methodNames) {
         if (throwable == null) {
             return null;
         }
         if (methodNames == null) {
             final Throwable cause = throwable.getCause();
             if (cause != null) {
                 return cause;
             }
             methodNames = CAUSE_METHOD_NAMES;
         }
         return Stream.of(methodNames).map(m -> getCauseUsingMethodName(throwable, m)).filter(Objects::nonNull).findFirst().orElse(null);
     }
 
     /**
      * Gets a {@link Throwable} by method name.
      *
      * @param throwable  the exception to examine.
      * @param methodName  the name of the method to find and invoke.
      * @return the wrapped exception, or {@code null} if not found.
      */
     // TODO: Remove in Lang 4
     private static Throwable getCauseUsingMethodName(final Throwable throwable, final String methodName) {
         if (methodName != null) {
             final Method method = MethodUtils.getMethodObject(throwable.getClass(), methodName);
             if (method != null && Throwable.class.isAssignableFrom(method.getReturnType())) {
                 try {
                     return (Throwable) method.invoke(throwable);
                 } catch (final ReflectiveOperationException ignored) {
                     // exception ignored
                 }
             }
         }
         return null;
     }
 
     /**
      * Gets the default names used when searching for the cause of an exception.
      *
      * <p>This may be modified and used in the overloaded getCause(Throwable, String[]) method.</p>
      *
      * @return cloned array of the default method names.
      * @since 3.0
      * @deprecated This feature will be removed in Lang 4.
      */
     @Deprecated
     public static String[] getDefaultCauseMethodNames() {
         return ArrayUtils.clone(CAUSE_METHOD_NAMES);
     }
 
     /**
      * Gets a short message summarizing the exception.
      * <p>
      * The message returned is of the form
      * {ClassNameWithoutPackage}: {ThrowableMessage}
      * </p>
      *
      * @param th  the throwable to get a message for, null returns empty string.
      * @return the message, non-null.
      * @since 2.2
      */
     public static String getMessage(final Throwable th) {
         if (th == null) {
             return StringUtils.EMPTY;
         }
         final String clsName = ClassUtils.getShortClassName(th, null);
         return clsName + ": " + StringUtils.defaultString(th.getMessage());
     }
 
     /**
      * Walks the {@link Throwable} to obtain its root cause.
      *
      * <p>This method walks through the exception chain until the last element,
      * the root cause of the chain, using {@link Throwable#getCause()}, and
      * returns that exception.</p>
      *
      * <p>This method handles recursive cause chains that might
      * otherwise cause infinite loops. The cause chain is processed until
      * the end, or until the next item in the chain is already
      * processed. If we detect a loop, then return the element before the loop.</p>
      *
      * @param throwable  the throwable to get the root cause for, may be null.
      * @return the root cause of the {@link Throwable},
      *  {@code null} if null throwable input.
      */
     public static Throwable getRootCause(final Throwable throwable) {
         final List<Throwable> list = getThrowableList(throwable);
         return list.isEmpty() ? null : list.get(list.size() - 1);
     }
 
     /**
      * Gets a short message summarizing the root cause exception.
      * <p>
      * The message returned is of the form
      * {ClassNameWithoutPackage}: {ThrowableMessage}
      * </p>
      *
      * @param throwable  the throwable to get a message for, null returns empty string.
      * @return the message, non-null.
      * @since 2.2
      */
     public static String getRootCauseMessage(final Throwable throwable) {
         final Throwable root = getRootCause(throwable);
         return getMessage(root == null ? throwable : root);
     }
 
     /**
      * Gets a compact stack trace for the root cause of the supplied
      * {@link Throwable}.
      *
      * <p>The output of this method is consistent across JDK versions.
      * It consists of the root exception followed by each of its wrapping
      * exceptions separated by '[wrapped]'. Note that this is the opposite
      * order to the JDK1.4 display.</p>
      *
      * @param throwable  the throwable to examine, may be null.
      * @return an array of stack trace frames, never null.
      * @since 2.0
      */
     public static String[] getRootCauseStackTrace(final Throwable throwable) {
         return getRootCauseStackTraceList(throwable).toArray(ArrayUtils.EMPTY_STRING_ARRAY);
     }
 
     /**
      * Gets a compact stack trace for the root cause of the supplied {@link Throwable}.
      *
      * <p>
      * The output of this method is consistent across JDK versions. It consists of the root exception followed by each of
      * its wrapping exceptions separated by '[wrapped]'. Note that this is the opposite order to the JDK1.4 display.
      * </p>
      *
      * @param throwable the throwable to examine, may be null.
      * @return a list of stack trace frames, never null.
      * @since 3.13.0
      */
     public static List<String> getRootCauseStackTraceList(final Throwable throwable) {
         if (throwable == null) {
             return Collections.emptyList();
         }
         final Throwable[] throwables = getThrowables(throwable);
         final int count = throwables.length;
         final List<String> frames = new ArrayList<>();
         List<String> nextTrace = getStackFrameList(throwables[count - 1]);
         for (int i = count; --i >= 0;) {
             final List<String> trace = nextTrace;
             if (i != 0) {
                 nextTrace = getStackFrameList(throwables[i - 1]);
                 removeCommonFrames(trace, nextTrace);
             }
             if (i == count - 1) {
                 frames.add(throwables[i].toString());
             } else {
                 frames.add(WRAPPED_MARKER + throwables[i].toString());
             }
             frames.addAll(trace);
         }
         return frames;
     }
 
     /**
      * Gets a {@link List} of stack frames, the message
      * is not included. Only the trace of the specified exception is
      * returned, any caused by trace is stripped.
      *
      * <p>This works in most cases and will only fail if the exception
      * message contains a line that starts with: {@code "<whitespace>at"}.</p>
      *
      * @param throwable is any throwable.
      * @return List of stack frames.
      */
     static List<String> getStackFrameList(final Throwable throwable) {
         final String stackTrace = getStackTrace(throwable);
         final String linebreak = System.lineSeparator();
         final StringTokenizer frames = new StringTokenizer(stackTrace, linebreak);
         final List<String> list = new ArrayList<>();
         boolean traceStarted = false;
         while (frames.hasMoreTokens()) {
             final String token = frames.nextToken();
             // Determine if the line starts with "<whitespace>at"
             final int at = token.indexOf("at");
             if (at != NOT_FOUND && token.substring(0, at).trim().isEmpty()) {
                 traceStarted = true;
                 list.add(token);
             } else if (traceStarted) {
                 break;
             }
         }
         return list;
     }
 
     /**
      * Gets an array where each element is a line from the argument.
      *
      * <p>The end of line is determined by the value of {@link System#lineSeparator()}.</p>
      *
      * @param stackTrace  a stack trace String.
      * @return an array where each element is a line from the argument.
      */
     static String[] getStackFrames(final String stackTrace) {
         return new IterableStringTokenizer(stackTrace, System.lineSeparator()).toArray();
     }
 
     /**
      * Gets the stack trace associated with the specified
      * {@link Throwable} object, decomposing it into a list of
      * stack frames.
      *
      * <p>
      * The result of this method vary by JDK version as this method
      * uses {@link Throwable#printStackTrace(java.io.PrintWriter)}.
      * </p>
      *
      * @param throwable  the {@link Throwable} to examine, may be null.
      * @return an array of strings describing each stack frame, never null.
      */
     public static String[] getStackFrames(final Throwable throwable) {
         if (throwable == null) {
             return ArrayUtils.EMPTY_STRING_ARRAY;
         }
         return getStackFrames(getStackTrace(throwable));
     }
 
     /**
      * Gets the stack trace from a Throwable as a String, including suppressed and cause exceptions.
      *
      * <p>
      * The result of this method vary by JDK version as this method
      * uses {@link Throwable#printStackTrace(java.io.PrintWriter)}.
      * </p>
      *
      * @param throwable  the {@link Throwable} to be examined, may be null.
      * @return the stack trace as generated by the exception's
      * {@code printStackTrace(PrintWriter)} method, or an empty String if {@code null} input.
      */
     public static String getStackTrace(final Throwable throwable) {
         if (throwable == null) {
             return StringUtils.EMPTY;
         }
         final StringWriter sw = new StringWriter();
         throwable.printStackTrace(new PrintWriter(sw, true));
         return sw.toString();
     }
 
     /**
      * Gets a count of the number of {@link Throwable} objects in the
      * exception chain.
      *
      * <p>A throwable without cause will return {@code 1}.
      * A throwable with one cause will return {@code 2} and so on.
      * A {@code null} throwable will return {@code 0}.</p>
      *
      * <p>This method handles recursive cause chains
      * that might otherwise cause infinite loops. The cause chain is
      * processed until the end, or until the next item in the
      * chain is already in the result.</p>
      *
      * @param throwable  the throwable to inspect, may be null.
      * @return the count of throwables, zero on null input.
      */
     public static int getThrowableCount(final Throwable throwable) {
         return getThrowableList(throwable).size();
     }
 
     /**
      * Gets the list of {@link Throwable} objects in the
      * exception chain.
      *
      * <p>A throwable without cause will return a list containing
      * one element - the input throwable.
      * A throwable with one cause will return a list containing
      * two elements. - the input throwable and the cause throwable.
      * A {@code null} throwable will return a list of size zero.</p>
      *
      * <p>This method handles recursive cause chains that might
      * otherwise cause infinite loops. The cause chain is processed until
      * the end, or until the next item in the chain is already
      * in the result list.</p>
      *
      * @param throwable  the throwable to inspect, may be null.
      * @return the list of throwables, never null.
      * @since 2.2
      */
     public static List<Throwable> getThrowableList(Throwable throwable) {
         final List<Throwable> list = new ArrayList<>();
         while (throwable != null && !list.contains(throwable)) {
             list.add(throwable);
             throwable = throwable.getCause();
         }
         return list;
     }
 
     /**
      * Gets the list of {@link Throwable} objects in the
      * exception chain.
      *
      * <p>A throwable without cause will return an array containing
      * one element - the input throwable.
      * A throwable with one cause will return an array containing
      * two elements. - the input throwable and the cause throwable.
      * A {@code null} throwable will return an array of size zero.</p>
      *
      * <p>This method handles recursive cause chains
      * that might otherwise cause infinite loops. The cause chain is
      * processed until the end, or until the next item in the
      * chain is already in the result array.</p>
      *
      * @param throwable  the throwable to inspect, may be null.
      * @return the array of throwables, never null.
      * @see #getThrowableList(Throwable)
      */
     public static Throwable[] getThrowables(final Throwable throwable) {
         return getThrowableList(throwable).toArray(ArrayUtils.EMPTY_THROWABLE_ARRAY);
     }
 
     /**
      * Tests if the throwable's causal chain have an immediate or wrapped exception
      * of the given type?
      *
      * @param chain
      *            The root of a Throwable causal chain.
      * @param type
      *            The exception type to test.
      * @return true, if chain is an instance of type or is an
      *         UndeclaredThrowableException wrapping a cause.
      * @since 3.5
      * @see #wrapAndThrow(Throwable)
      */
     public static boolean hasCause(Throwable chain,
             final Class<? extends Throwable> type) {
         if (chain instanceof UndeclaredThrowableException) {
             chain = chain.getCause();
         }
         return type.isInstance(chain);
     }
 
     /**
      * Worker method for the {@code indexOfType} methods.
      *
      * @param throwable the throwable to inspect, may be null.
      * @param type      the type to search for, subclasses match, null returns -1.
      * @param fromIndex the (zero-based) index of the starting position, negative treated as zero, larger than chain size returns -1.
      * @param subclass  if {@code true}, compares with {@link Class#isAssignableFrom(Class)}, otherwise compares using references.
      * @return index of the {@code type} within throwables nested within the specified {@code throwable}.
      */
     private static int indexOf(final Throwable throwable, final Class<? extends Throwable> type, int fromIndex, final boolean subclass) {
         if (throwable == null || type == null) {
             return NOT_FOUND;
         }
         if (fromIndex < 0) {
             fromIndex = 0;
         }
         final Throwable[] throwables = getThrowables(throwable);
         if (fromIndex >= throwables.length) {
             return NOT_FOUND;
         }
         if (subclass) {
             for (int i = fromIndex; i < throwables.length; i++) {
                 if (type.isAssignableFrom(throwables[i].getClass())) {
                     return i;
                 }
             }
         } else {
             for (int i = fromIndex; i < throwables.length; i++) {
                 if (type.equals(throwables[i].getClass())) {
                     return i;
                 }
             }
         }
         return NOT_FOUND;
     }
 
     /**
      * Returns the (zero-based) index of the first {@link Throwable}
      * that matches the specified class (exactly) in the exception chain.
      * Subclasses of the specified class do not match - see
      * {@link #indexOfType(Throwable, Class)} for the opposite.
      *
      * <p>A {@code null} throwable returns {@code -1}.
      * A {@code null} type returns {@code -1}.
      * No match in the chain returns {@code -1}.</p>
      *
      * @param throwable  the throwable to inspect, may be null.
      * @param clazz  the class to search for, subclasses do not match, null returns -1.
      * @return the index into the throwable chain, -1 if no match or null input.
      */
     public static int indexOfThrowable(final Throwable throwable, final Class<? extends Throwable> clazz) {
         return indexOf(throwable, clazz, 0, false);
     }
 
     /**
      * Returns the (zero-based) index of the first {@link Throwable} that matches the specified type in the exception chain from a specified index. Subclasses
      * of the specified class do not match - see {@link #indexOfType(Throwable, Class, int)} for the opposite.
      *
      * <p>
      * A {@code null} throwable returns {@code -1}. A {@code null} type returns {@code -1}. No match in the chain returns {@code -1}. A negative start index is
      * treated as zero. A start index greater than the number of throwables returns {@code -1}.
      * </p>
      *
      * @param throwable the throwable to inspect, may be null.
      * @param clazz     the class to search for, subclasses do not match, null returns -1.
      * @param fromIndex the (zero-based) index of the starting position, negative treated as zero, larger than chain size returns -1.
      * @return the index into the throwable chain, -1 if no match or null input.
      */
     public static int indexOfThrowable(final Throwable throwable, final Class<? extends Throwable> clazz, final int fromIndex) {
         return indexOf(throwable, clazz, fromIndex, false);
     }
 
     /**
      * Returns the (zero-based) index of the first {@link Throwable}
      * that matches the specified class or subclass in the exception chain.
      * Subclasses of the specified class do match - see
      * {@link #indexOfThrowable(Throwable, Class)} for the opposite.
      *
      * <p>A {@code null} throwable returns {@code -1}.
      * A {@code null} type returns {@code -1}.
      * No match in the chain returns {@code -1}.</p>
      *
      * @param throwable  the throwable to inspect, may be null.
      * @param type  the type to search for, subclasses match, null returns -1.
      * @return the index into the throwable chain, -1 if no match or null input.
      * @since 2.1
      */
     public static int indexOfType(final Throwable throwable, final Class<? extends Throwable> type) {
         return indexOf(throwable, type, 0, true);
     }
 
     /**
      * Returns the (zero-based) index of the first {@link Throwable} that matches the specified type in the exception chain from a specified index. Subclasses
      * of the specified class do match - see {@link #indexOfThrowable(Throwable, Class)} for the opposite.
      *
      * <p>
      * A {@code null} throwable returns {@code -1}. A {@code null} type returns {@code -1}. No match in the chain returns {@code -1}. A negative start index is
      * treated as zero. A start index greater than the number of throwables returns {@code -1}.
      * </p>
      *
      * @param throwable the throwable to inspect, may be null.
      * @param type      the type to search for, subclasses match, null returns -1.
      * @param fromIndex the (zero-based) index of the starting position, negative treated as zero, larger than chain size returns -1.
      * @return the index into the throwable chain, -1 if no match or null input.
      * @since 2.1
      */
     public static int indexOfType(final Throwable throwable, final Class<? extends Throwable> type, final int fromIndex) {
         return indexOf(throwable, type, fromIndex, true);
     }
 
     /**
      * Checks if a throwable represents a checked exception
      *
      * @param throwable
      *            The throwable to check.
      * @return True if the given Throwable is a checked exception.
      * @since 3.13.0
      */
     public static boolean isChecked(final Throwable throwable) {
         return throwable != null && !(throwable instanceof Error) && !(throwable instanceof RuntimeException);
     }
 
     /**
      * Checks if a throwable represents an unchecked exception
      *
      * @param throwable
      *            The throwable to check.
      * @return True if the given Throwable is an unchecked exception.
      * @since 3.13.0
      */
     public static boolean isUnchecked(final Throwable throwable) {
         return throwable != null && (throwable instanceof Error || throwable instanceof RuntimeException);
     }
 
     /**
      * Prints a compact stack trace for the root cause of a throwable
      * to {@code System.err}.
      * <p>
      * The compact stack trace starts with the root cause and prints
      * stack frames up to the place where it was caught and wrapped.
      * Then it prints the wrapped exception and continues with stack frames
      * until the wrapper exception is caught and wrapped again, etc.
      * </p>
      * <p>
      * The output of this method is consistent across JDK versions.
      * </p>
      * <p>
      * The method is equivalent to {@code printStackTrace} for throwables
      * that don't have nested causes.
      * </p>
      *
      * @param throwable  the throwable to output.
      * @since 2.0
      */
     public static void printRootCauseStackTrace(final Throwable throwable) {
         printRootCauseStackTrace(throwable, System.err);
     }
 
     /**
      * Prints a compact stack trace for the root cause of a throwable.
      *
      * <p>The compact stack trace starts with the root cause and prints
      * stack frames up to the place where it was caught and wrapped.
      * Then it prints the wrapped exception and continues with stack frames
      * until the wrapper exception is caught and wrapped again, etc.</p>
      *
      * <p>The output of this method is consistent across JDK versions.
      * Note that this is the opposite order to the JDK1.4 display.</p>
      *
      * <p>The method is equivalent to {@code printStackTrace} for throwables
      * that don't have nested causes.</p>
      *
      * @param throwable  the throwable to output, may be null.
      * @param printStream  the stream to output to, may not be null.
      * @throws NullPointerException if the printStream is {@code null}.
      * @since 2.0
      */
     @SuppressWarnings("resource")
     public static void printRootCauseStackTrace(final Throwable throwable, final PrintStream printStream) {
         if (throwable == null) {
             return;
         }
         Objects.requireNonNull(printStream, "printStream");
         getRootCauseStackTraceList(throwable).forEach(printStream::println);
         printStream.flush();
     }
 
     /**
      * Prints a compact stack trace for the root cause of a throwable.
      *
      * <p>The compact stack trace starts with the root cause and prints
      * stack frames up to the place where it was caught and wrapped.
      * Then it prints the wrapped exception and continues with stack frames
      * until the wrapper exception is caught and wrapped again, etc.</p>
      *
      * <p>The output of this method is consistent across JDK versions.
      * Note that this is the opposite order to the JDK1.4 display.</p>
      *
      * <p>The method is equivalent to {@code printStackTrace} for throwables
      * that don't have nested causes.</p>
      *
      * @param throwable  the throwable to output, may be null.
      * @param printWriter  the writer to output to, may not be null.
      * @throws NullPointerException if the printWriter is {@code null}.
      * @since 2.0
      */
     @SuppressWarnings("resource")
     public static void printRootCauseStackTrace(final Throwable throwable, final PrintWriter printWriter) {
         if (throwable == null) {
             return;
         }
         Objects.requireNonNull(printWriter, "printWriter");
         getRootCauseStackTraceList(throwable).forEach(printWriter::println);
         printWriter.flush();
     }
 
     /**
      * Removes common frames from the cause trace given the two stack traces.
      *
      * @param causeFrames  stack trace of a cause throwable.
      * @param wrapperFrames  stack trace of a wrapper throwable.
      * @throws NullPointerException if either argument is null.
      * @since 2.0
      */
     public static void removeCommonFrames(final List<String> causeFrames, final List<String> wrapperFrames) {
         Objects.requireNonNull(causeFrames, "causeFrames");
         Objects.requireNonNull(wrapperFrames, "wrapperFrames");
         int causeFrameIndex = causeFrames.size() - 1;
         int wrapperFrameIndex = wrapperFrames.size() - 1;
         while (causeFrameIndex >= 0 && wrapperFrameIndex >= 0) {
             // Remove the frame from the cause trace if it is the same
             // as in the wrapper trace
             final String causeFrame = causeFrames.get(causeFrameIndex);
             final String wrapperFrame = wrapperFrames.get(wrapperFrameIndex);
             if (causeFrame.equals(wrapperFrame)) {
                 causeFrames.remove(causeFrameIndex);
             }
             causeFrameIndex--;
             wrapperFrameIndex--;
         }
     }
 
     /**
      * Throws the given (usually checked) exception without adding the exception to the throws
      * clause of the calling method. This method prevents throws clause
      * inflation and reduces the clutter of "Caused by" exceptions in the
      * stack trace.
      * <p>
      * The use of this technique may be controversial, but useful.
      * </p>
      * <pre>
      *  // There is no throws clause in the method signature.
      *  public int propagateExample() {
      *      try {
      *          // throws SomeCheckedException.
      *          return invocation();
      *      } catch (SomeCheckedException e) {
      *          // Propagates a checked exception and compiles to return an int.
      *          return ExceptionUtils.rethrow(e);
      *      }
      *  }
      * </pre>
      * <p>
      * This is an alternative to the more conservative approach of wrapping the
      * checked exception in a RuntimeException:
      * </p>
      * <pre>
      *  // There is no throws clause in the method signature.
      *  public int wrapExample() {
      *      try {
      *          // throws IOException.
      *          return invocation();
      *      } catch (Error e) {
      *          throw e;
      *      } catch (RuntimeException e) {
      *          // Throws an unchecked exception.
      *          throw e;
      *      } catch (Exception e) {
      *          // wraps a checked exception.
      *          throw new UndeclaredThrowableException(e);
      *      }
      *  }
      * </pre>
      * <p>
      * One downside to using this approach is that the Java compiler will not
      * allow invoking code to specify a checked exception in a catch clause
      * unless there is some code path within the try block that has invoked a
      * method declared with that checked exception. If the invoking site wishes
      * to catch the shaded checked exception, it must either invoke the shaded
      * code through a method re-declaring the desired checked exception, or
      * catch Exception and use the {@code instanceof} operator. Either of these
      * techniques are required when interacting with non-Java JVM code such as
      * Jython, Scala, or Groovy, since these languages do not consider any
      * exceptions as checked.
      * </p>
      *
      * @param throwable
      *            The throwable to rethrow.
      * @param <T> The type of the return value.
      * @return Never actually returns, this generic type matches any type
      *         which the calling site requires. "Returning" the results of this
      *         method, as done in the propagateExample above, will satisfy the
      *         Java compiler requirement that all code paths return a value.
      * @since 3.5
      * @see #wrapAndThrow(Throwable)
      */
     public static <T> T rethrow(final Throwable throwable) {
         // claim that the typeErasure invocation throws a RuntimeException
         return ExceptionUtils.<T, RuntimeException>eraseType(throwable);
     }
 
     /**
      * Streams causes of a Throwable.
      * <p>
      * A throwable without cause will return a stream containing one element - the input throwable. A throwable with one cause
      * will return a stream containing two elements. - the input throwable and the cause throwable. A {@code null} throwable
      * will return a stream of count zero.
      * </p>
      *
      * <p>
      * This method handles recursive cause chains that might otherwise cause infinite loops. The cause chain is
      * processed until the end, or until the next item in the chain is already in the result.
      * </p>
      *
      * @param throwable The Throwable to traverse.
      * @return A new Stream of Throwable causes.
      * @since 3.13.0
      */
     public static Stream<Throwable> stream(final Throwable throwable) {
         // No point building a custom Iterable as it would keep track of visited elements to avoid infinite loops
         return getThrowableList(throwable).stream();
     }
 
     /**
      * Worker method for the {@code throwableOfType} methods.
      *
      * @param <T> the type of Throwable you are searching.
      * @param throwable  the throwable to inspect, may be null.
      * @param type  the type to search, subclasses match, null returns null.
      * @param fromIndex  the (zero-based) index of the starting position,
      *  negative treated as zero, larger than chain size returns null.
      * @param subclass if {@code true}, compares with {@link Class#isAssignableFrom(Class)}, otherwise compares
      * using references.
      * @return throwable of the {@code type} within throwables nested within the specified {@code throwable}.
      */
     private static <T extends Throwable> T throwableOf(final Throwable throwable, final Class<T> type, int fromIndex, final boolean subclass) {
         if (throwable == null || type == null) {
             return null;
         }
         if (fromIndex < 0) {
             fromIndex = 0;
         }
         final Throwable[] throwables = getThrowables(throwable);
         if (fromIndex >= throwables.length) {
             return null;
         }
         if (subclass) {
             for (int i = fromIndex; i < throwables.length; i++) {
                 if (type.isAssignableFrom(throwables[i].getClass())) {
                     return type.cast(throwables[i]);
                 }
             }
         } else {
             for (int i = fromIndex; i < throwables.length; i++) {
                 if (type.equals(throwables[i].getClass())) {
                     return type.cast(throwables[i]);
                 }
             }
         }
         return null;
     }
 
     /**
      * Returns the first {@link Throwable}
      * that matches the specified class (exactly) in the exception chain.
      * Subclasses of the specified class do not match - see
      * {@link #throwableOfType(Throwable, Class)} for the opposite.
      *
      * <p>A {@code null} throwable returns {@code null}.
      * A {@code null} type returns {@code null}.
      * No match in the chain returns {@code null}.</p>
      *
      * @param <T> the type of Throwable you are searching.
      * @param throwable  the throwable to inspect, may be null.
      * @param clazz  the class to search for, subclasses do not match, null returns null.
      * @return the first matching throwable from the throwable chain, null if no match or null input.
      * @since 3.10
      */
     public static <T extends Throwable> T throwableOfThrowable(final Throwable throwable, final Class<T> clazz) {
         return throwableOf(throwable, clazz, 0, false);
     }
 
     /**
      * Returns the first {@link Throwable} that matches the specified type in the exception chain from a specified index. Subclasses of the specified class do
      * not match - see {@link #throwableOfType(Throwable, Class, int)} for the opposite.
      *
      * <p>
      * A {@code null} throwable returns {@code null}. A {@code null} type returns {@code null}. No match in the chain returns {@code null}. A negative start
      * index is treated as zero. A start index greater than the number of throwables returns {@code null}.
      * </p>
      *
      * @param <T>       the type of Throwable you are searching.
      * @param throwable the throwable to inspect, may be null.
      * @param clazz     the class to search for, subclasses do not match, null returns null.
      * @param fromIndex the (zero-based) index of the starting position, negative treated as zero, larger than chain size returns null.
      * @return the first matching throwable from the throwable chain, null if no match or null input.
      * @since 3.10
      */
     public static <T extends Throwable> T throwableOfThrowable(final Throwable throwable, final Class<T> clazz, final int fromIndex) {
         return throwableOf(throwable, clazz, fromIndex, false);
     }
 
     /**
      * Returns the throwable of the first {@link Throwable}
      * that matches the specified class or subclass in the exception chain.
      * Subclasses of the specified class do match - see
      * {@link #throwableOfThrowable(Throwable, Class)} for the opposite.
      *
      * <p>A {@code null} throwable returns {@code null}.
      * A {@code null} type returns {@code null}.
      * No match in the chain returns {@code null}.</p>
      *
      * @param <T> the type of Throwable you are searching.
      * @param throwable  the throwable to inspect, may be null.
      * @param type  the type to search for, subclasses match, null returns null.
      * @return the first matching throwable from the throwable chain, null if no match or null input.
      * @since 3.10
      */
     public static <T extends Throwable> T throwableOfType(final Throwable throwable, final Class<T> type) {
         return throwableOf(throwable, type, 0, true);
     }
 
     /**
      * Returns the first {@link Throwable} that matches the specified type in the exception chain from a specified index. Subclasses of the specified class do
      * match - see {@link #throwableOfThrowable(Throwable, Class)} for the opposite.
      *
      * <p>
      * A {@code null} throwable returns {@code null}. A {@code null} type returns {@code null}. No match in the chain returns {@code null}. A negative start
      * index is treated as zero. A start index greater than the number of throwables returns {@code null}.
      * </p>
      *
      * @param <T>       the type of Throwable you are searching.
      * @param throwable the throwable to inspect, may be null.
      * @param type      the type to search for, subclasses match, null returns null.
      * @param fromIndex the (zero-based) index of the starting position, negative treated as zero, larger than chain size returns null.
      * @return the first matching throwable from the throwable chain, null if no match or null input.
      * @since 3.10
      */
     public static <T extends Throwable> T throwableOfType(final Throwable throwable, final Class<T> type, final int fromIndex) {
         return throwableOf(throwable, type, fromIndex, true);
     }
 
     /**
      * Tests whether the specified {@link Throwable} is unchecked and throws it if so.
      *
      * @param <T> The Throwable type.
      * @param throwable the throwable to test and throw or return.
      * @return the given throwable.
      * @since 3.13.0
      * @deprecated Use {@link #throwUnchecked(Throwable)}.
      */
     @Deprecated
     public static <T> T throwUnchecked(final T throwable) {
         if (throwable instanceof RuntimeException) {
             throw (RuntimeException) throwable;
         }
         if (throwable instanceof Error) {
             throw (Error) throwable;
         }
         return throwable;
     }
 
     /**
      * Tests whether the specified {@link Throwable} is unchecked and throws it if so.
      *
      * @param <T> The Throwable type.
      * @param throwable the throwable to test and throw or return.
      * @return the given throwable.
      * @since 3.14.0
      */
     public static <T extends Throwable> T throwUnchecked(final T throwable) {
         if (isUnchecked(throwable)) {
             throw asRuntimeException(throwable);
         }
         return throwable;
     }
 
     /**
      * Throws a checked exception without adding the exception to the throws
      * clause of the calling method. For checked exceptions, this method throws
      * an UndeclaredThrowableException wrapping the checked exception. For
      * Errors and RuntimeExceptions, the original exception is rethrown.
      * <p>
      * The downside to using this approach is that invoking code which needs to
      * handle specific checked exceptions must sniff up the exception chain to
      * determine if the caught exception was caused by the checked exception.
      * </p>
      *
      * @param throwable
      *            The throwable to rethrow.
      * @param <R> The type of the returned value.
      * @return Never actually returned, this generic type matches any type
      *         which the calling site requires. "Returning" the results of this
      *         method will satisfy the Java compiler requirement that all code
      *         paths return a value.
      * @since 3.5
      * @see #asRuntimeException(Throwable)
      * @see #hasCause(Throwable, Class)
      */
     public static <R> R wrapAndThrow(final Throwable throwable) {
         throw new UndeclaredThrowableException(throwUnchecked(throwable));
     }
 
     /**
      * Public constructor allows an instance of {@link ExceptionUtils} to be created, although that is not
      * normally necessary.
      *
      * @deprecated TODO Make private in 4.0.
      */
     @Deprecated
     public ExceptionUtils() {
         // empty
     }
 }