this应用总结

1、使用this调用本类中的属性

class Person{
    private String name;
    private int age;
    public Person(String name,int age){
        this.name = name;
        this.age = age;
    }
    public String getInfo(){
        return name + ";;;;" + age;
    }
}

public class ThisDemo02 {
    public static void main(String[] args) {
        Person per1 = new Person("zhangsan", 30);
        System.out.println(per1.getInfo());
    }

}

输出结果为：zhangsan;;;;30

2、使用this调用构造方法

　　如果一个类中有多个构造方法，也可以利用this关键字互相调用；

　　注意：构造方法是在实例化对象时被自动调用的，也就是说在类中的所有方法中，只有构造方法是被优先调用的，所以使用this调用构造方法必须也只有放在构造方法的第一行。

class Person{
    private String name;
    private int age;
    public Person(){
        System.out.println("一个新的Person对象被实例化。");
    }
    public Person(String name,int age){
        this();
        this.name = name;
        this.age = age;
    }
    public String getInfo(){
        return name + ";;;;" + age;
    }
}

public class ThisDemo02 {
    public static void main(String[] args) {
        Person per1 = new Person("zhangsan", 30);
        System.out.println(per1.getInfo());
    }
}

输出结果为：

一个新的Person对象被实例化。
zhangsan;;;;30

3、this表示当前对象

class Person{
    public String getInfo(){
        System.out.println("Person类" + this);
        return null;
    }
}

public class ThisDemo02 {
    public static void main(String[] args) {
        Person per1 = new Person();
        Person per2 = new Person();
        System.out.println("main方法" + per1);
        per1.getInfo();
        System.out.println("....................." );
        System.out.println("main方法" + per2);
        per2.getInfo();
    }
}

输出结果为：

main方法thisdemo.Person@1db9742
Person类thisdemo.Person@1db9742
.....................
main方法thisdemo.Person@106d69c
Person类thisdemo.Person@106d69c

4、判断对象是否相等

　　方法一、

class Person{
    private String name;
    private int age;
    public  Person(String name,int age){
        this.setName(name);
        this.setAge(age);
    }
    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;
    }
    
}

public class ThisDemo02 {
    public static void main(String[] args) {
        Person per1 = new Person("zhangsan",30);
        Person per2 = new Person("zhangsan",30);
        if(per1.getName().equals(per2.getName()) && per2.getAge() == per2.getAge()){
            System.out.println("两个对象相等");
        }else{
            System.out.println("两个对象不相等");
        }    
    }
}

输出结果为：两个对象相等

 　　方法二

class Person{
    private String name;
    private int age;
    public  Person(String name,int age){
        this.setName(name);
        this.setAge(age);
    }
    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;
    }
    public boolean compare(Person per){
        Person p1 = this;
        Person p2 = per;
        
        if(p1 == p2){
            return true;
        }
        if(p1.name.equals(p2.name) && (p1.age == p2.age)){
            return true;
        }else{
            return false;
        }    
        
    }
}

public class ThisDemo02 {
    public static void main(String[] args) {
        Person per1 = new Person("zhangsan",30);
        Person per2 = new Person("zhangsan",3);
        if(per1.compare(per2)){
            System.out.println("两个对象相等");
        }else{
            System.out.println("两个对象不相等.........");
        }
    }
}

输出结果为：两个对象不相等.........

5、

public class Tester {
    int var;
    Tester(double var) {
        this.var = (int) var;
    }
    Tester(int var) {
        this("hello");
    }
    Tester(String s) {
        this();
        System.out.println(s);
    }
    public Tester() {
        System.out.println("googbay");
    }
    public static void main(String[] args) {
        Tester t = new Tester(5);
    }
}

输出结果为：

googbay
hello