如何在java中使用“this”关键字？

Question

我一直在使用多种方法，但是我的“java 完整参考”一书并没有很好地解释如何使用“this”关键字。

Answer 1

this in java

It is used to refer to the data members of the object in the envoked method or constructor in case there is a name conflict between fields and local variables

    public class Test {
    String s;
    int i; 
    public Test(String s, int i){
        this.s = s;
        this.i = i;
    } }

It is used to invoke one constructor from another constructor of the same class or you can say constructor chaining.

public class ConstructorChainingEg{
    String s;
    int i;
    public ConstructorChainingEg(String s, int i){
        this.s = s;
        this.i = i;
        System.out.println(s+" "+i);
    }
    public ConstructorChainingEg(){
        this("abc",3); // from here call goes to parameterized constructor
    }

    public static void main(String[] args) {
       ConstructorChainingEg m = new ConstructorChainingEg();
      // call goes to default constructor
    }
}

It also facilitates method chaining

class Swapper{
    int a,b;
    public Swapper(int a,int b){
        this.a=a;
        this.b=b;
    }
    public Swapper swap() {
        int c=this.a;
        this.a=this.b;
        this.b=c;
        return this;
    }
    public static void main(String aa[]){
        new Swapper(4,5).swap(); //method chaining
    }
}

Answer 2

Here's a couple:

public class Example {
    private int a;
    private int b;

    // use it to differentiate between local and class variables
    public Example(int a, int b) {
        this.a = a;
        this.b = b;
    }

    // use it to chain constructors
    public Example() {
        this(0, 0);
    }

    // revised answer:
    public int getA() {
        return this.a;
    }

    public int getB() {
        return this.b
    }

    public int setA(int a) {
        this.a = a
    }

    public void setB(int b) {
        this.b = b;
    }
}

this refers to the attributes that belong to the object in which this is used in. For example:

Example ex1 = new Example(3,4);
Example ex2 = new Example(8,1);

In these cases, ex1.getA() will return 3, because this is referring to the a that belongs to the object named ex1 , and not ex2 or anything else. The same goes for ex2.getB() .

If you look at the setA() and setB() methods, using this distinguishes the attributes a and b belonging to the object from the parameter names as they're the same.