标签：rip 创建 inf wap end his width span turn
程序设计语言中，将参数传递给方法（或函数）有两种方法。按值传递（call by value）表示方法接受的是调用者提供的值；按引用调用（call by reference）表示方法接受的是调用者提供的变量地址。Java程序设计语言都是采用按值传递。下面通过例题进行说明：
1 public class ParamTest {
2 public static void main(String[] args) {
3 /*
4 *Test1: Methods can‘t modify numeric parameters
5 */
6 System.out.println("Testing tripleValue:");
7 double percent = 10;
8 System.out.println("Before: percent=" + percent);
9 tripleValue(percent);
10 System.out.println("After: percent=" + percent);
11
12 /*
13 *Test2: Methods can change the state of object parameters
14 */
15 System.out.println("\nTesting tripleSalary");
16 Employee harry = new Employee("Harry", 50000);
17 System.out.println("Before: salary=" + harry.getSalary());
18 tripleSalary(harry);
19 System.out.println("After: salary=" + harry.getSalary());
20
21 /*
22 *Test3: Methods can‘t attach new objects to object parameters
23 */
24 System.out.println("\nTesting swap");
25 Employee a = new Employee("Alice", 30000);
26 Employee b = new Employee("Bob", 60000);
27 System.out.println("Before: a=" + a.getName());
28 System.out.println("Before: b=" + b.getName());
29 swap(a, b);
30 System.out.println("After: a=" + a.getName());
31 System.out.println("After: b=" + b.getName());
32 }
33
34 public static void tripleValue(double x) {
35 x *= 3;
36 System.out.println("End of method: x=" + x);
37 }
38
39 public static void tripleSalary(Employee x) {
40 x.raiseSalary(200);
41 System.out.println("End of method: salary=" + x.getSalary());
42 }
43
44 public static void swap(Employee x, Employee y) {
45 Employee temp = x;
46 x = y;
47 y = temp;
48 System.out.println("End of method: x=" + x.getName());
49 System.out.println("End of method: y=" + y.getName());
50 }
51 }
52
53 class Employee {
54 private String name;
55 private double salary;
56 public Employee(){}
57 public Employee(String name, double salary){
58 this.name = name;
59 this.salary = salary;
60 }
61
62 public String getName() {
63 return name;
64 }
65
66 public double getSalary() {
67 return salary;
68 }
69
70 public void raiseSalary(double byPercent){
71 double raise = salary * byPercent / 100;
72 salary += raise;
73 }
74 }
程序运行结果为：
从以上例题可以总结Java中方法参数的使用情况：
以上内容均参考：java核心技术 卷1 第十版 4.5节
———————————————————————————————————————————
下面通过画内存图说明参数传递过程：
基本数据类型的传递：
对象或数组作为参数传递：
标签：rip 创建 inf wap end his width span turn
原文地址：https://www.cnblogs.com/yang91/p/9633923.html
