【Java补充】Java方法参数

public class Main {

    public static void main(String[] args) {
        System.out.println("Hello World!");

        //Test1
        System.out.println("Test1");
        double percent = 10;
        System.out.println("befor percent=" + percent);
        tripleValue(percent);
        System.out.println("After percent" + percent);

        //Text2
        System.out.println("Text2");
        Employee harry = new Employee("Harry", 500);
        System.out.println("befor salary" + harry.getSalary());
        tripleSalary1(harry);
        System.out.println("After salary" + harry.getSalary());

        System.out.println("Text3");
        Employee harry2 = new Employee("Harry", 500);
        System.out.println("befor salary" + harry2.getSalary());
        tripleSalary2(harry2);
        System.out.println("After salary" + harry2.getSalary());

        //Text4
        System.out.println("Test4");
        System.out.println("\nTest4:");
        Employee a = new Employee("Alice", 70000);
        Employee b = new Employee("Bob", 60000);
        System.out.println("Before: a=" + a.getName());
        System.out.println("Before: b=" + b. getName());
        swap(a, b);
        System.out.println("After: a=" + a.getName());
        System.out.println("After: b=" + b.getName());
    }

    public static void tripleValue(double x) {
        x=x*3;
        System.out.println("End of method x=" + x);
    }

    public static void tripleSalary1(Employee x) {
        x.raiseSalary(200);
        System.out.println("End of method: salary=" + x.getSalary());

    }
    public static void tripleSalary2(Employee x) {
        double a=x.getSalary();
        a=a*3;
        x.setSalary(a);
        System.out.println("End of method: salary=" + x.getSalary());

    }

    public static void swap(Employee x, Employee y) {
        Employee temp=x;
        x=y;
        y=temp;
        System.out.println("End of method: x=" + x.getName());
        System.out.println("End of method: y=" + y.getName());

    }
}
class  Employee{
    private  String name;
    private  double salary;

    public Employee(String name, double salary) {
        this.name = name;
        this.salary = salary;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public void raiseSalary(double byPercent) {
        double raise=salary*byPercent/100;
        salary=raise;
    }
}

运行结果

Hello World!
Test1
befor percent=10.0
End of method x=30.0
After percent10.0
Text2
befor salary500.0
End of method: salary=1000.0
After salary1000.0
Text3
befor salary500.0
End of method: salary=1500.0
After salary1500.0
Test4

Test4:
Before: a=Alice
Before: b=Bob
End of method: x=Bob
End of method: y=Alice
After: a=Alice
After: b=Bob

---

在这个程序中， 首先试图将一个值参数的值
提高两倍，但没有成功：

Testing tripleValue:
Before: percent=10.0
End of method: x:30.0
After: percent=10.0

随后， 成功地将一个雇员的薪金提高了两倍：

Testing tripleSalary:
Before: salary=50000.0
End of method: salary=150000.0
After: salary=150000.0

方法结束之后， harry 引用的对象状态发生了改变。这是因为这个方法可以通过对象引用
的拷贝修改所引用的对象状态。
最后，程序演示了 swap 方法的失败效果：

Testing swap:
Before: a=Alice
Before: b=Bob
End of method: x=Bob
End of method: y=Alice
After: a=Alice
After: b=Bob

可以看出， 参数变量 X 和 y 交换了， 但是变量 a 和 b 没有受到影响。

图示.jpg