do java interface have to be abstract methods only code example

Example 1: abstract classes and interfaces in java

abstract class have no implementation of methods functions inside it. the classes which extending abstract class have to implement it

Example 2: can abstract class have non abstract methods in java

abstract class AbstractDemo { // Abstract class
   private int i = 0;
   public void display() { // non-abstract method
      System.out.print("Welcome to Tutorials Point");
   }
}
public class InheritedClassDemo extends AbstractDemo {
   public static void main(String args[]) {
      AbstractDemo demo = new InheritedClassDemo();
      demo.display();
   }
}