abstract keyword in java code example
Example 1: abstract class in java
Sometimes we may come across a situation where we cannot provide
implementation to all the methods in a class. We want to leave the
implementation to a class that extends it. In such case we declare a class
as abstract.To make a class abstract we use key word abstract.
Any class that contains one or more abstract methods is declared as abstract.
If we don’t declare class as abstract which contains abstract methods we get
compile time error.
1)Abstract classes cannot be instantiated
2)An abstarct classes contains abstract method, concrete methods or both.
3)Any class which extends abstarct class must override all methods of abstract
class
4)An abstarct class can contain either 0 or more abstract method.
Example 2: 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 3: how to make abstract method in java
public abstract class Account {
protected int accountNumber;
protected Customer customerObj;
protected double balance;
public Account(int saccountNumber, Customer scustomerObj,double sbalance){
accountNumber = saccountNumber;
customerObj = scustomerObj;
balance = sbalance;
}
public abstract boolean withdraw(double amount);
}
public class SavingsAccount extends Account {
private double minimumBalance;
public SavingsAccount(int saccountNumber, Customer scustomerObj, double sbalance, double sminimumBalance) {
super(saccountNumber, scustomerObj, sbalance);
minimumBalance = sminimumBalance;
}
public boolean withdraw(double amount) {
if (balance() > minimumBalance && balance() - amount > minimumBalance) {
super.setBalance(balance() - amount);
return true;
} else {
return false;
}
}
}
Example 4: java abstract class
abstract class Shape
{
abstract void sides();
}
class Triangle extends Shape
{
void sides()
{
System.out.println("Triangle shape has three sides.");
}
}
class Pentagon extends Shape
{
void sides()
{
System.out.println("Pentagon shape has five sides.");
}
public static void main(String[] args)
{
Triangle obj1 = new Triangle();
obj1.sides();
Pentagon obj2 = new Pentagon();
obj2.sides();
}
}
Example 5: abstract class in java
public abstract class GraphicObject {
abstract void draw();
}
Example 6: how to create an abstract method in java
abstract class Scratch{
abstract public void hello();
abstract String randNum();
}
interface Other{
public void bye();
String randDouble();
}