20.22

java.lang.Throwable

 and its Subclasses

THE PACKAGE JAVA.LANG

By convention, class

Throwable

 and all its subclasses have two constructors,

one that takes no arguments and one that takes a

String

 argument that can be

used to produce an error message. This is true of all the classes shown above, with

one exception:

ExceptionInInitializerError

. These predefined classes oth 

erwise have no new content; they merely inherit methods from class

Throwable

.

public class Throwable {

public Throwable();

public Throwable(String message);

public String toString();

public String getMessage();

public Throwable fillInStackTrace();

public void printStackTrace();

public void printStackTrace(java.io.PrintStream s);

}

20.22.1

public Throwable()

This constructor initializes a newly created

Throwable

 object with

null

 as its

error message string. Also, the method

fillInStackTrace

 ( 20.22.5) is called

for this object.

20.22.2

public Throwable(String message)

This constructor initializes a newly created

Throwable

 object by saving a refer 

ence to the error message string

s

 for later retrieval by the

getMessage

 method

( 20.22.3). Also, the method

fillInStackTrace

 ( 20.22.5) is called for this

object.

20.22.3

public String getMessage()

If this

Throwable

 object was created with an error message string ( 20.22.2),

then a reference to that string is returned.

If this

Throwable

 object was created with no error message string ( 20.22.1),

then

null

 is returned.

20.22.4

public String toString()

If this

Throwable

 object was created with an error message string ( 20.22.2),

then the result is the concatenation of three strings:

612