JAVA EE: Java Tutorial : Java unchecked exception(NullPointerException and NumberFormatException)

Friday 17 June 2016

Java Tutorial : Java unchecked exception(NullPointerException and NumberFormatException)

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Java Tutorial : Java unchecked exception(NullPointerException and NumberFormatException)

UnCheckedExceptionDemo1.java

/*
 * If you compile this code, it would compile
 * successfully however when you will run it, it would
 * throw NullPointerException. That clearly shows that
 * unchecked exceptions are not checked at compile-time,
 * they are being checked at runtime.
 */

public class UnCheckedExceptionDemo1
{
    public static void main(String[] args)
    {
        String str = null;
        /*
         * str is null, so it should throw
         * NullPointerException
         */
        System.out.println(str.isEmpty());
        System.out.println("Normal flow...");
    }

}

Output

Exception in thread "main" java.lang.NullPointerException
    at UnCheckedExceptionDemo1.main(UnCheckedExceptionDemo1.java:18)

UnCheckedExceptionDemo2.java

/*
 * If you compile this code, it would compile
 * successfully however when you will run it, it would
 * throw NumberFormatException. That clearly shows that
 * unchecked exceptions are not checked at compile-time,
 * they are being checked at runtime.
 */

public class UnCheckedExceptionDemo2
{
    public static void main(String[] args)
    {
        String str = "abc";
        /*
         * str is "abc", so it should throw
         * NumberFormatException
         */
        int i=Integer.parseInt(str);
        System.out.println(i);
        System.out.println("Normal flow...");
    }

}

Output

Exception in thread "main" java.lang.NumberFormatException: For input string: "abc"
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    at java.lang.Integer.parseInt(Integer.java:580)
    at java.lang.Integer.parseInt(Integer.java:615)
    at UnCheckedExceptionDemo2.main(UnCheckedExceptionDemo2.java:18)