Java初学几个程序背诵

1.Hello world

class first
{
    public static void main(String[] args){
        System.out.println("Hello world");
    }
}

2.数组 -> for循环

 class first
 {
     public static void main(String[] args){
         int[] array;
         array = new int[5];
         for(int i=0;i<5;i++){
             array[i]=i;
         }
         for(int i=4;i>=0;i--){
             System.out.println(array[i]);
         }
     }
 }

3.简单的类:class

 class first
 {
     public static void main(String[] args){
         Human Person = new Human() ;
         Person.age();
         System.out.println(Person.height);
     }
 }
 class Human
 {
     void age(){
         System.out.println("I am 12");
     }
     int height = 10;
 }

4.构造函数

 class first
 {
     public static void main(String[] args){
         Human Person = new Human(180) ;
         Person.age();
         System.out.println(Person.height);
     }
 }
 class Human
 {
     public Human(int h){
         this.height =h;
         System.out.println("I am SmarTop");
     }
     void age(){
         System.out.println("I am 12");
     }
     int height = 10;
 }

5.重载

 class first
 {
     public static void main(String[] args){
         Human Person = new Human(180,"SmarTop") ;
         Person.age();
         System.out.println(Person.height);
     }
 }
 class Human
 {
     public Human(int h){
         this.height =h;
         System.out.println("I am SmarTop");
     }
     Human(int h , String name){
         this.height = h;
         this.name = name;
         System.out.println("Name:"+name+"\nHeight:"+h);
     }
     void age(){
         System.out.println("I am 2");
     }
     int height = 10;
     String name;
 }

6.封装和接口

class two
{
    public static void main(String[] args){
        Human aPerson = new Human(160);
        System.out.println(aPerson.getHeight());
        aPerson.growHeight(170);
        System.out.println(aPerson.getHeight());
        aPerson.replaceBreath(100);
    }
}
class Human
{
    public Human(int h){
        this.height = h;
        System.out.println("I am born");
    }
    public int getHeight(){
        return this.height;
    }
    public void growHeight(int h){
        this.height = this.height + h;
    }
    private void breath(){
        System.out.println("I am nicia");
    }
    public void replaceBreath(int rep){
        int i;
        for(i=0;i<rep;i++){
            this.breath();
        }
    }
    private int height;
}