Java中this关键字的4种用法详解(附常见面试题)

public class Student {
    private String name; // 成员变量
    
    public void setName(String name) { // 局部变量
        name = name; // 这里会出现问题
    }
}

public class Student {
    private String name; // 成员变量
    
    public void setName(String name) { // 局部变量
        this.name = name; // 使用this明确指定成员变量
    }
    
    public String getName() {
        return this.name; // 这里this可省略，但显式使用更清晰
    }
}

public class Rectangle {
    private int width;
    private int height;
    private String color;
    
    // 无参构造
    public Rectangle() {
        this(10, 20, "black"); // 调用三参构造
    }
    
    // 两参构造
    public Rectangle(int width, int height) {
        this(width, height, "black"); // 调用三参构造
    }
    
    // 三参构造（主构造方法）
    public Rectangle(int width, int height, String color) {
        this.width = width;
        this.height = height;
        this.color = color;
    }
}

public class Button {
    private List<ClickListener> listeners = new ArrayList<>();
    
    public void addClickListener(ClickListener listener) {
        listeners.add(listener);
    }
    
    public void click() {
        // 模拟点击事件
        for (ClickListener listener : listeners) {
            listener.onClick(this); // 将当前Button对象传递给监听器
        }
    }
}

interface ClickListener {
    void onClick(Button button);
}

public class PersonBuilder {
    private String firstName;
    private String lastName;
    private int age;
    
    public PersonBuilder withFirstName(String firstName) {
        this.firstName = firstName;
        return this;
    }
    
    public PersonBuilder withLastName(String lastName) {
        this.lastName = lastName;
        return this;
    }
    
    public PersonBuilder withAge(int age) {
        this.age = age;
        return this;
    }
    
    public Person build() {
        return new Person(firstName, lastName, age);
    }
}

// 使用示例
Person person = new PersonBuilder()
    .withFirstName("张")
    .withLastName("三")
    .withAge(30)
    .build();

public class Car {
    private String model;
    private int year;
    private String color;
    private double price;
    
    // 无参构造调用全参构造
    public Car() {
        this("Unknown", 2023, "White", 0.0);
    }
    
    // 三参构造调用全参构造
    public Car(String model, int year, String color) {
        this(model, year, color, 0.0);
    }
    
    // 全参构造（主构造方法）
    public Car(String model, int year, String color, double price) {
        this.model = model;
        this.year = year;
        this.color = color;
        this.price = price;
    }
    
    // 使用this区分成员变量
    public void setModel(String model) {
        this.model = model;
    }
    
    // 返回this实现链式调用
    public Car withYear(int year) {
        this.year = year;
        return this;
    }
    
    // 传递当前对象
    public void printInfo(Printer printer) {
        printer.print(this);
    }
    
    // 省略getter方法...
}

interface Printer {
    void print(Car car);
}

+----------------+       +----------------+
|     Car        |       |    Printer     |
+----------------+       +----------------+
| - model: String|<>-----| + print(Car):  |
| - year: int    |       |    void        |
| - color: String|       +----------------+
| - price: double|
+----------------+
| + Car()        |
| + Car(model,   |
|   year, color) |
| + Car(model,   |
|   year, color, |
|   price)       |
| + setModel()   |
| + withYear():  |
|   Car          |
| + printInfo()  |
+----------------+

public class Example {
    private int value;
    
    public static void staticMethod() {
        // this.value = 10; // 编译错误
    }
}