Constructors
Every class you create has a constructor, even if you don't write one.
/**
* Constructor use the class name and has no return type.
* You could have more than one constructor in a class.
*/
package com.minte9.oop.constructors;
public class Constructors {
public static void main(String[] args) {
new A().test();
new B("aaa");
new B(100);
/*
Default constructor used
Constructor 1 - aaa
Constructor 2 - 100
*/
}
}
class A {
/*
public Output() {
// default constructor
}
*/
public void test() {
System.out.println("Default constructor used");
}
}
class B {
public B(String s) {
System.out.println("Constructor 1 - " + s);
}
public B(int i) {
System.out.println("Constructor 2 - " + i);
}
}
This
To call another constructor from the same class use this() method.
/**
* To call another constructor from the same class ...
* use this() method.
*/
package com.minte9.oop.constructors;
public class This {
public static void main(String[] args) {
Rectangle a = new Rectangle();
Rectangle b = new Rectangle(100, 200);
Rectangle c = new Rectangle(300, 400, 11, 22); // Look Here
System.out.println(a);
System.out.println(b);
System.out.println(c);
/*
W: 0 H: 0 x: 0 y: 0
W: 100 H: 200 x: 0 y: 0
W: 300 H: 400 x: 11 y: 22
*/
}
}
class Rectangle {
private int x, y;
private int width, height;
public Rectangle() {
this(0, 0, 0, 0); // Look Here
}
public Rectangle(int width, int height) {
this.width = width;
this.height = height;
}
public Rectangle(int width, int height, int x, int y) {
this(width, height);
this.x = x;
this.y = y;
}
public String toString() {
return String.format(
"W: %s H: %s x: %s y: %s", width, height, x, y
);
}
}
Last update: 444 days ago
