封装

信息隐藏,隐藏对象的细节

访问修饰符

public

private

protected

默认

属性封装的实现

方法封装的目的(隐藏方法实现细节)

package com.tanlei.newer;

public class TeacherDemo {

public static void main(String[] args) {

teacher t=new teacher();

//t.name("zhangs");

t.setName("zhangs");

t.setAge(23);

System.out.println(t.getAge());

}

}

class teacher{

private String name;

private int age;

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public int getAge() {

return age;

}

public void setAge(int age) {

if( age<25) {

System.out.println("年龄太小了");

this.age=age;

}else {

this.age=age;

}

}

}

UML类图(建模语言,图形化语言)

类的构造方法

对属性进行初始化赋值

new 操作符 {自动调用}

package com.tanlei.newer;

public class ContstructorDemo {

public static void main(String[] args) {

person person=new person("长沙",3);

//在堆中开辟空间,给属性分配默认的初始值

//假设属性一开始就赋值了,就进行赋值工作

//调用构造方法来进行赋值

System.out.println(person.toString());

}

}

class person{

private String name;

private int age;

public person(String name,int a) {

this.name=name;

this.age=a;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public int getAge() {

return age;

}

public void setAge(int age) {

this.age = age;

}

@Override

public String toString() {

return "person [name=" + name + ", age=" + age + "]";

}

}

static关键字

类变量(静态变量)

类方法(静态方法)

优先于对象的存在

可以通过类名.成员调用

package com.tanlei.newer;

public class Static {

public static void main(String[] args) {

Account.num1++;

System.out.println(Account.num1);

}

}

class Account{

public static int num1=1;//静态变量

public int num2=2;

public void shownum1() {

System.out.println(num1);

}

public void shownum2() {

System.out.println(num2);

}

}

//static语句块 类被加载的时候就会执行,只会执行一次,优先于构造方法的执行

static {

}