The initCause() method of Throwable class is used to initialize the cause of this Throwable with the specified cause passed as a parameter to initCause(). Actually, the cause is throwable that caused this throwable Object to get thrown when an exception occurs. This method can be called only once. Generally, This method is called from within the constructor, or immediately after creating the throwable. If the calling Throwable is created by using Throwable(Throwable) or Throwable(String, Throwable), then this method cannot be called even once.
Syntax:
public Throwable initCause?(Throwable cause)
Parameters: This method accepts cause as a parameter which represents the cause of this Throwable.
Returns: This method returns a reference to this Throwable instance.
Exception: This method throws:
- IllegalArgumentException if cause is this throwable.
- IllegalStateException if this throwable was created with Throwable(Throwable) or Throwable(String, Throwable), or this method has already been called on this throwable.
Below programs illustrate the initCause method of Throwable class:
Example 1:
Java
// Java program to demonstrate// the initCause() Method.import java.io.*;class GFG { // Main Method public static void main(String[] args) throws Exception { try { testException1(); } catch (Throwable e) { System.out.println("Cause : " + e.getCause()); } } // method which throws Exception public static void testException1() throws Exception { // ArrayIndexOutOfBoundsException // This exception will be used as a Cause // of another exception ArrayIndexOutOfBoundsException ae = new ArrayIndexOutOfBoundsException(); // create a new Exception Exception ioe = new Exception(); // initialize the cause and throw Exception ioe.initCause(ae); throw ioe; }} |
Cause : java.lang.ArrayIndexOutOfBoundsException
Example 2:
Java
// Java program to demonstrate// the initCause() Method.import java.io.*;class GFG { // Main Method public static void main(String[] args) throws Exception { try { // add the numbers addPositiveNumbers(2, -1); } catch (Throwable e) { System.out.println("Cause : " + e.getCause()); } } // method which adds two positive number public static void addPositiveNumbers(int a, int b) throws Exception { // if Numbers are Positive // than add or throw Exception if (a < 0 || b < 0) { // create a Exception // when Numbers are not Positive // This exception will be used as a Cause // of another exception Exception ee = new Exception("Numbers are not Positive"); // create a new Exception Exception anotherEXe = new Exception(); // initialize the cause and throw Exception anotherEXe.initCause(ee); throw anotherEXe; } else { System.out.println(a + b); } }} |
Cause : java.lang.Exception: Numbers are not Positive
References: https://docs.oracle.com/javase/10/docs/api/java/lang/Throwable.html#initCause(java.lang.Throwable)
