this是什么?
什么时候使用?
当在方法内需要用到调用该方法的对象时,就用this。例如:
public class Person{
String name;
int age;
public Person(String name,int age){
//此时,为了明确形参和成员变量,需要使用this
this.name = name;
this.age = age
}
public void setName(String name){
//同样的,在方法中,也需要辨别
this.name = name;
}
public String getName(){
return this.name;
}
}
同时,在构造器中使用this需要遵从以下原则:
Person.java
package myjava;
public class Person {
private String name;
private int age;
public Person() {}
public Person(int age) {
this.age = age;
}
public Person(String name) {
this();//这个this()实际上调用的是Person()
this.name = name;
}
public Person(String name, int age) {
this(age);//这个this(age)实际上调用的是Person(int age)
this.name = name;
}
public void setName(String name) {
this.name = name;
}
public String getName() {
return this.name;
}
public void setAge(int age) {
this.age = age;
}
public int getAge() {
return this.age;
}
}
Test.java
package myjava;
public class Test {
public static void main(String[] args) {
Person p = new Person();
p.setAge(20);
p.setName("tom");
int age = p.getAge();
String name = p.getName();
System.out.println("name:"+name);
System.out.println("age:"+age);
Person p1 = new Person(10);
String name1 = p1.getName();
int age1 = p1.getAge();
System.out.println("name1:"+name1);
System.out.println("age1:"+age1);
Person p2 = new Person("jack");
String name2 = p2.getName();
int age2 = p2.getAge();
System.out.println("name2:"+name2);
System.out.println("age2:"+age2);
Person p3 = new Person("bob",30);
String name3 = p3.getName();
int age3 = p3.getAge();
System.out.println("name3:"+name3);
System.out.println("age3:"+age3);
}
}
最后输出:
说明:新建一个对象时,根据传的参数的不同(类型或者个数),java会调用相应的构造方法。在构造方法中,通过this(参数),又会调用其它的构造方法。