Java Throwable initCause() method

The initCause() method of Java Throwable class is used to initialize the cause of the calling Throwable with the specified cause. This method can be called only once. If the calling Throwable is created by using Throwable(Throwable) or Throwable(String, Throwable), then this method cannot be called even once.

Syntax

Parameter

A Throwable instance returned by getCause() method, which is to be initialized to the calling Throwable as a cause.

Return

A reference to the calling Throwable's instance.

Example 1

import java.io.IOException;
public class ThrowableInitCauseExample1 {
    public static void main(String[] args) throws Exception {
   try{
       throwableTest();
   }catch(Exception e){
    System.err.println("Cause : "+e.getCause());   
   }
   }
public static void throwableTest() throws Exception{
        try{
       int i=4/0;
   }catch(ArithmeticException ae){
      IOException ioe = new IOException();
                    ioe.initCause(ae);
		throw ioe;
    }
}
}

Output:

Cause : java.lang.ArithmeticException: / by zero

Example 2

public class ThrowableInitCauseExample2 {
    public static void main(String[] args)throws Throwable {
   try{
       func1();
   }catch(Exception e){
       System.out.println("Cause : "+e.getCause());
   }
   
}
    public static void func1() throws javaException{
        try{
            func2();
        }catch(newException n){
            javaException j1 = new javaException();
            j1.initCause(n);
            throw j1;
        }
    }
    public static void func2() throws newException{
        throw new newException();
    }
}    
    class javaException extends Throwable{
        javaException(){
            super("This is new java Exception!!");
        }
    }
    class newException extends Throwable{
    newException(){
        super("This is another new exception!!");
    }
}

Output:

Exception in thread "main" javaException: This is new java Exception!!
	at ThrowableInitCauseExample2.func1(ThrowableInitCauseExample2.java:14)
	at ThrowableInitCauseExample2.main(ThrowableInitCauseExample2.java:4)
Caused by: newException: This is another new exception!!
	at ThrowableInitCauseExample2.func2(ThrowableInitCauseExample2.java:20)
	at ThrowableInitCauseExample2.func1(ThrowableInitCauseExample2.java:12)
	... 1 more

Next TopicJava-throwable-printstacktrace-method

← prev next →