nullpointerexception

1TestObject a = new TestObject();String b = a.getTestResult();b.toString();

1Integer num;
2num = new Integer(10);
3

1int x;
2x = 10;
3

1public class MyClass{
2private Object iAmNowNull;//This is null by default
3    private Object iAmInitialized=new Object();
4    public void test(){
5    	System.out.println(iAmInitialized.toString());//prints that object
6        System.out.println(iAmNull.toString());//throws a NullPointerException
7}

1public class MyClass{
2	private Object iAmNull;//This is null by default
3    private Object iAmInitialized=new Object();
4    public void test(){
5    	System.out.println(iAmInitialized.toString());//prints that object
6        System.out.println(iAmNull.toString());//throws a NullPointerException
7    }
8}