Throwable getCause() method in Java with Examples

The getCause() method of the Throwable class is used to retrieve the original cause of an exception. If no cause is associated with the exception, it returns null.

• It is mainly used in exception chaining to identify the root cause of an error.
• Methods like printStackTrace() internally use getCause() to display nested exception details.

Example 1: Exception Chaining with initCause()

class GFG {
    public static void main(String[] args) {
        try {
            divide(2, 0);
        } catch (ArithmeticException e) {
            System.out.println("Cause of Exception: " + e.getCause());
        }
    }
    public static void divide(int a, int b) throws Exception {
        try {
            int result = a / b;
        } catch (ArithmeticException e) {
            // Creating a new exception and setting the cause
            ArithmeticException newEx = new ArithmeticException("Division failed");
            newEx.initCause(e);
            throw newEx;
        }
    }
}

Cause of Exception: java.lang.ArithmeticException: / by zero

Explanation:

• The original ArithmeticException caused by division by zero is set as the cause of a new ArithmeticException.
• Calling getCause() retrieves the original exception.

Syntax

public Throwable getCause()

Return Value: Returns the Throwable that caused this exception, or null if the cause is unknown.Class:

How getCause() Works

• When an exception is created, it can optionally reference another exception as its cause.
• The cause can be set during construction or later using the initCause(Throwable cause) method.
• Calling getCause() on an exception returns the underlying cause.

Example 2: Without Exception Chaining

class GFG {
    public static void main(String[] args) {
        try {
            divide(2, 0);
        } catch (ArithmeticException e) {
            System.out.println("Cause of Exception: " + e.getCause());
        }
    }
    public static void divide(int a, int b) throws Exception {
        int result = a / b; // Throws ArithmeticException directly
    }
}

Cause of Exception : null

Explanation: Here, no cause was explicitly set, so getCause() returns null.

Key Points:

• getCause() helps debug chained exceptions by identifying the root cause.
• Use initCause(Throwable cause) to link exceptions manually.
• Always check for null to avoid NullPointerException.