what is an abstract method ? code example

Example 1: What are abstract methods in java

An abstract method is the method which does’nt have any body. 
Abstract method is declared with
keyword abstract and semicolon in place of method body.

  public abstract void <method name>();
Ex : public abstract void getDetails();
It is the responsibility of subclass to provide implementation to 
abstract method defined in abstract class

Example 2: is it necessary for abstract class to have abstract method

No, abstract class can have zero abstract methods.

Example 3: how to make abstract method in java

public abstract class Account {		//abstract class //perent class
    protected int accountNumber;
    protected Customer customerObj;
    protected double balance;
  	//constructor
  	public Account(int saccountNumber, Customer scustomerObj,double sbalance){
        accountNumber = saccountNumber;
        customerObj = scustomerObj;
        balance = sbalance;
    }
  	// abstract Function
    public abstract boolean withdraw(double amount); 
}   

public class SavingsAccount extends Account { // child class
    private double minimumBalance;
  	// constructor
    public SavingsAccount(int saccountNumber, Customer scustomerObj, double sbalance, double sminimumBalance) {
        super(saccountNumber, scustomerObj, sbalance);
        minimumBalance = sminimumBalance;
    }
	// Implementation of abstract function in child class
    public boolean withdraw(double amount) {
        if (balance() > minimumBalance && balance() - amount > minimumBalance) {
            super.setBalance(balance() - amount);
            return true;
        } else {
            return false;
        }
    }
}

Example 4: abstract class in java

public abstract class GraphicObject {

   abstract void draw();
}

Example 5: how to create an abstract method in java

abstract class Scratch{
  // cannot be static
    abstract public void hello();
    abstract String randNum();
}

interface Other{
  //all methods in an interface are abstract
    public void bye();
    String randDouble();
}

Example 6: how panache handles abstract class in java

//interface declaration
interface Polygon_Shape {
    void calculateArea(int length, int breadth);
}
 
//implement the interface
class Rectangle implements Polygon_Shape {
    //implement the interface method
    public void calculateArea(int length, int breadth) {
        System.out.println("The area of the rectangle is " + (length * breadth));
    }
}
 
class Main {
    public static void main(String[] args) {
        Rectangle rect = new Rectangle();       //declare a class object
        rect.calculateArea(10, 20);             //call the method
    }
}