java，

java，

assign memory:

int p[];//only few default exit:int byte long....

p = new int[6];

//or

cat tt, pp;

int a, b;

tt=new cat();

pp=tt;//point to same area

a=b;//different area

main:

public class Main {
    public static void main(string[] args) {
        System.out.println("hello Java!");
    }
}

include:

<main>

import com.example.cat

<./com/example/cat.java>

package com.example

static:

var: counting the class

func: <classname>.<func> could call

多态:

条件:子父类,重写,方法,父类引用指向子类实际对象

非多态:重载,相同属性,由引用类型确定