Java class variables and class method instance analysis

1.static static variables

1.Static variables are shared by all objects of the same class

2.static class variables are generated and used when the class is loaded

static is saved at the end of the class instance, in the heap

3. It is a bit like C language C

package com.demo.static_;
import java.sql.SQLOutput;
public class childgeme {
    public static void main(String[] args) {
        Child ch01=new Child("牛牛牛");
        ch01.join();
        ch01.count++;
        Child ch02=new Child("马马马");
        ch02.join();
        ch02.count++;
        Child ch03=new Child("猪猪猪");
        ch03.join();
        ch03.count++;
        System.out.println("共有"+Child.count+"个小孩加入了游戏");
        System.out.println("ch01.count="+ch01.count);
        System.out.println("ch02.count="+ch02.count);
        System.out.println("ch03.count="+ch03.count);
    }
}
class Child{
    private String name;
    //定义一个变量count，是一个类变量（静态变量）
    public static int count=0;
    public Child(String name) {
        this.name = name;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public static int getCount() {
        return count;
    }
    public static void setCount(int count) {
        Child.count = count;
    }
    public void join(){
        System.out.println(this.name+"加入了游戏");
    }
}

2. Class variables (static variables Access)

The access rights and scope of static variables are the same as those of ordinary properties

package com.demo.static_;
import java.sql.SQLOutput;
public class visit_Static {
    public static void main(String[] args) {
        //1.类名.类变量名
        //static类变量在类加载的时候就生成使用
        System.out.println("A.name="+A.name);
        System.out.println("A.getAge()="+A.getAge());
        //2.类对象.类变量名
        A a=new A();
        System.out.println("a.name="+a.name);
        System.out.println("a.getAge()="+a.getAge());
    }
}
class A{
    //类变量
    public static String name="Demo龙";
    private static int age=99;
    public static int getAge() {
        return age;
    }
    public static void setAge(int age) {
        A.age = age;
    }
}

If the class variable is private, it cannot be accessed in the main function. Need to use class function to access

3. Class method

1. Class method is also called static method

2. Access modifier static data return type (){}

3.static access modifier data return type () {}

4. The calling method is the same as the class method

package com.demo.static_;
public class static_method {
    public static void main(String[] args) {
        stu a01=new stu("小虎");
        //stu.sumfee();
        a01.sumfee(150);
        stu a02=new stu("小龙");
        a02.sumfee(250);
        //stu.sumfee();
        stu a03=new stu("小猪");
        stu.sumfee(199);
        //输出当前收到的总学费
        stu.showfee();
    }
}
class stu{
    private String name;//普通成员
    //定义一个静态变量来累计学生的学费
    private static double fee=0;
    public stu(String name) {
        this.name = name;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    //当方法使用了static修饰后，该方法就是静态方法
    //静态方法就可以访问静态变量
    public static double getFee() {
        return fee;
    }
    public static void setFee(double fee) {
        stu.fee = fee;
    }
    public static void sumfee(double fee){
        stu.fee+=fee;
    }
    public static void showfee(){
        System.out.println("总学费="+stu.fee);
    }
}

detail

1. Static methods can only access static members, this/super are not allowed to be used in class methods

2. Non-static methods can access static members and non-static members

3. All comply with access permissions

The above is the detailed content of Java class variables and class method instance analysis. For more information, please follow other related articles on the PHP Chinese website!