What's the difference between an abstract class and a static one?

Question

Neither is instantiable. What are the differences, and in what situations might you use one or the other?

Answer 1

Abstract class main purpose is to define one or more abstract method(s). Any class extending Abstract class will implement the abstract method or else its also need to be declared as "Abstract".

But, its also possible to declare a class as "Abstract" without implementing any abstract method(s) in it. See the sample below.

public abstract class AbstractTest {

public void abcd(){}

public static void main(String[] args) {

      System.out.print("hi...");

}

}

Only inner class can be declared as "Static", see the code below. Upper/encapsulating class can't be declared as "Static". It can be accessed by using Upper/encapsulating class variable.Static-inner-classname i.e same as any static method invocation using class name.

public class StaticTest {

public static void main(String ag[]){
    System.out.println("hello...1");
    StaticTest.StaticTest2.meth2();
}

public static class StaticTest2 {
    public static void meth2(){
        System.out.print("hello...2");
    }
}

}