java call method from another class example

1public class method{
2  public static void sayHello(){
3    System.out.println("Hello World");
4  }
5}
6public class app{
7  public static void main(String[] args){
8    method m = new method(); // Creating an instance from our class
9    m.sayHello(); // using the class methods by the instance we created.
10  }
11}

11_ you should first create an instance from this class.
22_ once you create one, you use it for calling the class methods.

1class A { 
2  
3    public void a1 ( ) { 
4    } 
5 
6    private void a2 ( ) { 
7    } 
8} 
9 
10class B { 
11 
12    private A objA = new A ( ); 
13 
14    public void b1 ( ) { 
15        // Call to method a1. This works. 
16        objA.a1 (); 
17    } 
18 
19    void b2 ( ) { 
20        // Call to method a2. This will give compile error. 
21        objA.a2 (); 
22    } 
23} 

1public class Alpha {
2     public void DoSomethingAlpha() {
3          Beta cbeta = new Beta();
4          cbeta.DoSomethingBeta();  //?
5     }
6}
7

1public class Alpha extends Beta{
2     public void DoSomethingAlpha() {
3          DoSomethingBeta();  //?
4     }
5}
6

1Beta.DoSomethingBeta();
2