Instances of two subclasses, {@link java.lang.Error} and * {@link java.lang.Exception}, are conventionally used to indicate * that exceptional situations have occurred. Typically, these instances * are freshly created in the context of the exceptional situation so * as to include relevant information (such as stack trace data). * *
A throwable contains a snapshot of the execution stack of its * thread at the time it was created. It can also contain a message * string that gives more information about the error. Over time, a * throwable can {@linkplain Throwable#addSuppressed suppress} other * throwables from being propagated. Finally, the throwable can also * contain a cause: another throwable that caused this * throwable to be constructed. The recording of this causal information * is referred to as the chained exception facility, as the * cause can, itself, have a cause, and so on, leading to a "chain" of * exceptions, each caused by another. * *
One reason that a throwable may have a cause is that the class that * throws it is built atop a lower layered abstraction, and an operation on * the upper layer fails due to a failure in the lower layer. It would be bad * design to let the throwable thrown by the lower layer propagate outward, as * it is generally unrelated to the abstraction provided by the upper layer. * Further, doing so would tie the API of the upper layer to the details of * its implementation, assuming the lower layer's exception was a checked * exception. Throwing a "wrapped exception" (i.e., an exception containing a * cause) allows the upper layer to communicate the details of the failure to * its caller without incurring either of these shortcomings. It preserves * the flexibility to change the implementation of the upper layer without * changing its API (in particular, the set of exceptions thrown by its * methods). * *
A second reason that a throwable may have a cause is that the method * that throws it must conform to a general-purpose interface that does not * permit the method to throw the cause directly. For example, suppose * a persistent collection conforms to the {@link java.util.Collection * Collection} interface, and that its persistence is implemented atop * {@code java.io}. Suppose the internals of the {@code add} method * can throw an {@link java.io.IOException IOException}. The implementation * can communicate the details of the {@code IOException} to its caller * while conforming to the {@code Collection} interface by wrapping the * {@code IOException} in an appropriate unchecked exception. (The * specification for the persistent collection should indicate that it is * capable of throwing such exceptions.) * *
A cause can be associated with a throwable in two ways: via a * constructor that takes the cause as an argument, or via the * {@link #initCause(Throwable)} method. New throwable classes that * wish to allow causes to be associated with them should provide constructors * that take a cause and delegate (perhaps indirectly) to one of the * {@code Throwable} constructors that takes a cause. * * Because the {@code initCause} method is public, it allows a cause to be * associated with any throwable, even a "legacy throwable" whose * implementation predates the addition of the exception chaining mechanism to * {@code Throwable}. * *
By convention, class {@code Throwable} and its subclasses have two * constructors, one that takes no arguments and one that takes a * {@code String} argument that can be used to produce a detail message. * Further, those subclasses that might likely have a cause associated with * them should have two more constructors, one that takes a * {@code Throwable} (the cause), and one that takes a * {@code String} (the detail message) and a {@code Throwable} (the * cause). * * @author unascribed * @author Josh Bloch (Added exception chaining and programmatic access to * stack trace in 1.4.) * @jls 11.2 Compile-Time Checking of Exceptions * @since JDK1.0 */ @:require(java0) extern class Throwable implements java.io.Serializable { /** * Constructs a new throwable with {@code null} as its detail message. * The cause is not initialized, and may subsequently be initialized by a * call to {@link #initCause}. * *
The {@link #fillInStackTrace()} method is called to initialize * the stack trace data in the newly created throwable. */ @:overload public function new() : Void; /** * Constructs a new throwable with the specified detail message. The * cause is not initialized, and may subsequently be initialized by * a call to {@link #initCause}. * *
The {@link #fillInStackTrace()} method is called to initialize * the stack trace data in the newly created throwable. * * @param message the detail message. The detail message is saved for * later retrieval by the {@link #getMessage()} method. */ @:overload public function new(message : String) : Void; /** * Constructs a new throwable with the specified detail message and * cause.
Note that the detail message associated with * {@code cause} is not automatically incorporated in * this throwable's detail message. * *
The {@link #fillInStackTrace()} method is called to initialize * the stack trace data in the newly created throwable. * * @param message the detail message (which is saved for later retrieval * by the {@link #getMessage()} method). * @param cause the cause (which is saved for later retrieval by the * {@link #getCause()} method). (A {@code null} value is * permitted, and indicates that the cause is nonexistent or * unknown.) * @since 1.4 */ @:require(java4) @:overload public function new(message : String, cause : Throwable) : Void; /** * Constructs a new throwable with the specified cause and a detail * message of {@code (cause==null ? null : cause.toString())} (which * typically contains the class and detail message of {@code cause}). * This constructor is useful for throwables that are little more than * wrappers for other throwables (for example, {@link * java.security.PrivilegedActionException}). * *
The {@link #fillInStackTrace()} method is called to initialize * the stack trace data in the newly created throwable. * * @param cause the cause (which is saved for later retrieval by the * {@link #getCause()} method). (A {@code null} value is * permitted, and indicates that the cause is nonexistent or * unknown.) * @since 1.4 */ @:require(java4) @:overload public function new(cause : Throwable) : Void; /** * Constructs a new throwable with the specified detail message, * cause, {@linkplain #addSuppressed suppression} enabled or * disabled, and writable stack trace enabled or disabled. If * suppression is disabled, {@link #getSuppressed} for this object * will return a zero-length array and calls to {@link * #addSuppressed} that would otherwise append an exception to the * suppressed list will have no effect. If the writable stack * trace is false, this constructor will not call {@link * #fillInStackTrace()}, a {@code null} will be written to the * {@code stackTrace} field, and subsequent calls to {@code * fillInStackTrace} and {@link * #setStackTrace(StackTraceElement[])} will not set the stack * trace. If the writable stack trace is false, {@link * #getStackTrace} will return a zero length array. * *
Note that the other constructors of {@code Throwable} treat * suppression as being enabled and the stack trace as being * writable. Subclasses of {@code Throwable} should document any * conditions under which suppression is disabled and document * conditions under which the stack trace is not writable. * Disabling of suppression should only occur in exceptional * circumstances where special requirements exist, such as a * virtual machine reusing exception objects under low-memory * situations. Circumstances where a given exception object is * repeatedly caught and rethrown, such as to implement control * flow between two sub-systems, is another situation where * immutable throwable objects would be appropriate. * * @param message the detail message. * @param cause the cause. (A {@code null} value is permitted, * and indicates that the cause is nonexistent or unknown.) * @param enableSuppression whether or not suppression is enabled or disabled * @param writableStackTrace whether or not the stack trace should be * writable * * @see OutOfMemoryError * @see NullPointerException * @see ArithmeticException * @since 1.7 */ @:require(java7) @:overload private function new(message : String, cause : Throwable, enableSuppression : Bool, writableStackTrace : Bool) : Void; /** * Returns the detail message string of this throwable. * * @return the detail message string of this {@code Throwable} instance * (which may be {@code null}). */ @:overload public function getMessage() : String; /** * Creates a localized description of this throwable. * Subclasses may override this method in order to produce a * locale-specific message. For subclasses that do not override this * method, the default implementation returns the same result as * {@code getMessage()}. * * @return The localized description of this throwable. * @since JDK1.1 */ @:require(java1) @:overload public function getLocalizedMessage() : String; /** * Returns the cause of this throwable or {@code null} if the * cause is nonexistent or unknown. (The cause is the throwable that * caused this throwable to get thrown.) * *
This implementation returns the cause that was supplied via one of * the constructors requiring a {@code Throwable}, or that was set after * creation with the {@link #initCause(Throwable)} method. While it is * typically unnecessary to override this method, a subclass can override * it to return a cause set by some other means. This is appropriate for * a "legacy chained throwable" that predates the addition of chained * exceptions to {@code Throwable}. Note that it is not * necessary to override any of the {@code PrintStackTrace} methods, * all of which invoke the {@code getCause} method to determine the * cause of a throwable. * * @return the cause of this throwable or {@code null} if the * cause is nonexistent or unknown. * @since 1.4 */ @:require(java4) @:overload @:synchronized public function getCause() : Throwable; /** * Initializes the cause of this throwable to the specified value. * (The cause is the throwable that caused this throwable to get thrown.) * *
This method can be called at most once. It is generally called from * within the constructor, or immediately after creating the * throwable. If this throwable was created * with {@link #Throwable(Throwable)} or * {@link #Throwable(String,Throwable)}, this method cannot be called * even once. * *
An example of using this method on a legacy throwable type * without other support for setting the cause is: * *
* try {
* lowLevelOp();
* } catch (LowLevelException le) {
* throw (HighLevelException)
* new HighLevelException().initCause(le); // Legacy constructor
* }
*
*
* @param cause the cause (which is saved for later retrieval by the
* {@link #getCause()} method). (A {@code null} value is
* permitted, and indicates that the cause is nonexistent or
* unknown.)
* @return a reference to this {@code Throwable} instance.
* @throws IllegalArgumentException if {@code cause} is this
* throwable. (A throwable cannot be its own cause.)
* @throws IllegalStateException if this throwable was
* created with {@link #Throwable(Throwable)} or
* {@link #Throwable(String,Throwable)}, or this method has already
* been called on this throwable.
* @since 1.4
*/
@:require(java4) @:overload @:synchronized public function initCause(cause : Throwable) : Throwable;
/**
* Returns a short description of this throwable.
* The result is the concatenation of:
* * This example was produced by running the program: ** java.lang.NullPointerException * at MyClass.mash(MyClass.java:9) * at MyClass.crunch(MyClass.java:6) * at MyClass.main(MyClass.java:3) *
* class MyClass {
* public static void main(String[] args) {
* crunch(null);
* }
* static void crunch(int[] a) {
* mash(a);
* }
* static void mash(int[] b) {
* System.out.println(b[0]);
* }
* }
*
* The backtrace for a throwable with an initialized, non-null cause
* should generally include the backtrace for the cause. The format
* of this information depends on the implementation, but the following
* example may be regarded as typical:
* * HighLevelException: MidLevelException: LowLevelException * at Junk.a(Junk.java:13) * at Junk.main(Junk.java:4) * Caused by: MidLevelException: LowLevelException * at Junk.c(Junk.java:23) * at Junk.b(Junk.java:17) * at Junk.a(Junk.java:11) * ... 1 more * Caused by: LowLevelException * at Junk.e(Junk.java:30) * at Junk.d(Junk.java:27) * at Junk.c(Junk.java:21) * ... 3 more ** Note the presence of lines containing the characters {@code "..."}. * These lines indicate that the remainder of the stack trace for this * exception matches the indicated number of frames from the bottom of the * stack trace of the exception that was caused by this exception (the * "enclosing" exception). This shorthand can greatly reduce the length * of the output in the common case where a wrapped exception is thrown * from same method as the "causative exception" is caught. The above * example was produced by running the program: *
* public class Junk {
* public static void main(String args[]) {
* try {
* a();
* } catch(HighLevelException e) {
* e.printStackTrace();
* }
* }
* static void a() throws HighLevelException {
* try {
* b();
* } catch(MidLevelException e) {
* throw new HighLevelException(e);
* }
* }
* static void b() throws MidLevelException {
* c();
* }
* static void c() throws MidLevelException {
* try {
* d();
* } catch(LowLevelException e) {
* throw new MidLevelException(e);
* }
* }
* static void d() throws LowLevelException {
* e();
* }
* static void e() throws LowLevelException {
* throw new LowLevelException();
* }
* }
*
* class HighLevelException extends Exception {
* HighLevelException(Throwable cause) { super(cause); }
* }
*
* class MidLevelException extends Exception {
* MidLevelException(Throwable cause) { super(cause); }
* }
*
* class LowLevelException extends Exception {
* }
*
* As of release 7, the platform supports the notion of
* suppressed exceptions (in conjunction with the {@code
* try}-with-resources statement). Any exceptions that were
* suppressed in order to deliver an exception are printed out
* beneath the stack trace. The format of this information
* depends on the implementation, but the following example may be
* regarded as typical:
*
* * Exception in thread "main" java.lang.Exception: Something happened * at Foo.bar(Foo.java:10) * at Foo.main(Foo.java:5) * Suppressed: Resource$CloseFailException: Resource ID = 0 * at Resource.close(Resource.java:26) * at Foo.bar(Foo.java:9) * ... 1 more ** Note that the "... n more" notation is used on suppressed exceptions * just at it is used on causes. Unlike causes, suppressed exceptions are * indented beyond their "containing exceptions." * *
An exception can have both a cause and one or more suppressed * exceptions: *
* Exception in thread "main" java.lang.Exception: Main block * at Foo3.main(Foo3.java:7) * Suppressed: Resource$CloseFailException: Resource ID = 2 * at Resource.close(Resource.java:26) * at Foo3.main(Foo3.java:5) * Suppressed: Resource$CloseFailException: Resource ID = 1 * at Resource.close(Resource.java:26) * at Foo3.main(Foo3.java:5) * Caused by: java.lang.Exception: I did it * at Foo3.main(Foo3.java:8) ** Likewise, a suppressed exception can have a cause: *
* Exception in thread "main" java.lang.Exception: Main block * at Foo4.main(Foo4.java:6) * Suppressed: Resource2$CloseFailException: Resource ID = 1 * at Resource2.close(Resource2.java:20) * at Foo4.main(Foo4.java:5) * Caused by: java.lang.Exception: Rats, you caught me * at Resource2$CloseFailException.*/ @:overload public function printStackTrace() : Void; /** * Prints this throwable and its backtrace to the specified print stream. * * @param s {@code PrintStream} to use for output */ @:overload public function printStackTrace(s : java.io.PrintStream) : Void; /** * Prints this throwable and its backtrace to the specified * print writer. * * @param s {@code PrintWriter} to use for output * @since JDK1.1 */ @:require(java1) @:overload public function printStackTrace(s : java.io.PrintWriter) : Void; /** * Fills in the execution stack trace. This method records within this * {@code Throwable} object information about the current state of * the stack frames for the current thread. * *(Resource2.java:45) * ... 2 more *
If the stack trace of this {@code Throwable} {@linkplain * Throwable#Throwable(String, Throwable, boolean, boolean) is not * writable}, calling this method has no effect. * * @return a reference to this {@code Throwable} instance. * @see java.lang.Throwable#printStackTrace() */ @:overload @:synchronized public function fillInStackTrace() : Throwable; /** * Provides programmatic access to the stack trace information printed by * {@link #printStackTrace()}. Returns an array of stack trace elements, * each representing one stack frame. The zeroth element of the array * (assuming the array's length is non-zero) represents the top of the * stack, which is the last method invocation in the sequence. Typically, * this is the point at which this throwable was created and thrown. * The last element of the array (assuming the array's length is non-zero) * represents the bottom of the stack, which is the first method invocation * in the sequence. * *
Some virtual machines may, under some circumstances, omit one
* or more stack frames from the stack trace. In the extreme case,
* a virtual machine that has no stack trace information concerning
* this throwable is permitted to return a zero-length array from this
* method. Generally speaking, the array returned by this method will
* contain one element for every frame that would be printed by
* {@code printStackTrace}. Writes to the returned array do not
* affect future calls to this method.
*
* @return an array of stack trace elements representing the stack trace
* pertaining to this throwable.
* @since 1.4
*/
@:require(java4) @:overload public function getStackTrace() : java.NativeArray If the stack trace of this {@code Throwable} {@linkplain
* Throwable#Throwable(String, Throwable, boolean, boolean) is not
* writable}, calling this method has no effect other than
* validating its argument.
*
* @param stackTrace the stack trace elements to be associated with
* this {@code Throwable}. The specified array is copied by this
* call; changes in the specified array after the method invocation
* returns will have no affect on this {@code Throwable}'s stack
* trace.
*
* @throws NullPointerException if {@code stackTrace} is
* {@code null} or if any of the elements of
* {@code stackTrace} are {@code null}
*
* @since 1.4
*/
@:require(java4) @:overload public function setStackTrace(stackTrace : java.NativeArray The suppression behavior is enabled unless disabled
* {@linkplain #Throwable(String, Throwable, boolean, boolean) via
* a constructor}. When suppression is disabled, this method does
* nothing other than to validate its argument.
*
* Note that when one exception {@linkplain
* #initCause(Throwable) causes} another exception, the first
* exception is usually caught and then the second exception is
* thrown in response. In other words, there is a causal
* connection between the two exceptions.
*
* In contrast, there are situations where two independent
* exceptions can be thrown in sibling code blocks, in particular
* in the {@code try} block of a {@code try}-with-resources
* statement and the compiler-generated {@code finally} block
* which closes the resource.
*
* In these situations, only one of the thrown exceptions can be
* propagated. In the {@code try}-with-resources statement, when
* there are two such exceptions, the exception originating from
* the {@code try} block is propagated and the exception from the
* {@code finally} block is added to the list of exceptions
* suppressed by the exception from the {@code try} block. As an
* exception unwinds the stack, it can accumulate multiple
* suppressed exceptions.
*
* An exception may have suppressed exceptions while also being
* caused by another exception. Whether or not an exception has a
* cause is semantically known at the time of its creation, unlike
* whether or not an exception will suppress other exceptions
* which is typically only determined after an exception is
* thrown.
*
* Note that programmer written code is also able to take
* advantage of calling this method in situations where there are
* multiple sibling exceptions and only one can be propagated.
*
* @param exception the exception to be added to the list of
* suppressed exceptions
* @throws IllegalArgumentException if {@code exception} is this
* throwable; a throwable cannot suppress itself.
* @throws NullPointerException if {@code exception} is {@code null}
* @since 1.7
*/
@:require(java7) @:overload @:final @:synchronized public function addSuppressed(exception : Throwable) : Void;
/**
* Returns an array containing all of the exceptions that were
* suppressed, typically by the {@code try}-with-resources
* statement, in order to deliver this exception.
*
* If no exceptions were suppressed or {@linkplain
* #Throwable(String, Throwable, boolean, boolean) suppression is
* disabled}, an empty array is returned. This method is
* thread-safe. Writes to the returned array do not affect future
* calls to this method.
*
* @return an array containing all of the exceptions that were
* suppressed to deliver this exception.
* @since 1.7
*/
@:require(java7) @:overload @:final @:synchronized public function getSuppressed() : java.NativeArray