how to access public methods from another class java code example

Example 1: how to access methods from another class in java

public class Alpha {
     public void DoSomethingAlpha() {
          Beta cbeta = new Beta();
          cbeta.DoSomethingBeta();  //?
     }
}

Example 2: how to access methods from another class in java

public class Alpha extends Beta{
     public void DoSomethingAlpha() {
          DoSomethingBeta();  //?
     }
}