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
