为什么Java中的updateObject()方法中对象属性没有更新？ [复制]

Question

public class Employee {

    int age = 32;
    String name = "Kevin";

    public Employee updateEmployee(Employee e) {
        e = new Employee();
        e.age = 56;
        e.name = "Jeff";
        return e;
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Employee t = new Employee();
        t.updateEmployee(t);
        System.out.println("age= " + t.age + " " + "name= " + " " + t.name);

    }

}

====================

OUTPUT:-
age= 32 name=  Kevin

为什么输出不是 56 和 Jeff。我更新了方法中的对象引用“t”？请帮忙。

Answer 1

如果您在 IDE 中看到，您可能会收到来自 IDE 的警告，

updateEmployee() method

陈述，

The return value is not used anywhere, you can make the return type as void

由于Java始终是按值传递的，如果您需要更新对象的状态，则将返回（更新的）值赋回给它。

public static void main(String[] args) {
    Employee t = new Employee();
    t = t.updateEmployee(t);
    System.out.println("age= " + t.age + " " + "name= " + " " + t.name);
}

输出：

age= 56 name=  Jeff

Edit: 如果您的更新方法只适用于 this 参考，那就更好了。

public void updateEmployee() {
    this.age = 56;
    this.name = "Jeff";
}

public static void main(String[] args) {
    Employee t = new Employee();
    t.updateEmployee();
    System.out.println("age= " + t.age + " " + "name= " + " " + t.name);
}