Java是值传递（没有引用传递）！！！

柔情只为你懂 2022-09-04 00:53 30阅读 0赞

很多程序设计语言（特别是，C++和Pascal）提供了两种参数传递的方式：值调用和引用调用。有些程序员认为Java程序设计语言对对象采用的是引用调用，实际上，这种理解是不对的。由于这种误解具有一定的普遍性，所以下面给出一个反例来详细地阐述一下这个问题。  
  
  
  请问下面的employee1和employee2交换引用地址了吗？

public static void main(String[] args) { 
            Employee employee1 = new Employee("张三",1500);
            Employee employee2 = new Employee("李四",2000);
    
            System.out.printf("初始：employee1：%s,employee2：%s",employee1,employee2);
            swap(employee1, employee2);
            System.out.println();
            System.out.printf("swap后：employee1：%s,employee2：%s",employee1,employee2);
        }
    
        public static void swap(Employee e1, Employee e2) { 
            Employee temp = e1;
            e1 = e2;
            e2 = temp;
        }

完整代码如下：

package com.demo.test.demo.api;
    
    /** * 探究Java究竟是值传递还是引用传递 * * @author zhao.hualuo * Create at 2021/8/9 */
    public class ParameterDemo { 
    
        public static void main(String[] args) { 
            Employee employee1 = new Employee("张三",1500);
            Employee employee2 = new Employee("李四",2000);
    
            System.out.printf("初始：employee1：%s,employee2：%s",employee1,employee2);
            swap(employee1, employee2);
            System.out.println();
            System.out.printf("swap后：employee1：%s,employee2：%s",employee1,employee2);
        }
    
        public static void swap(Employee e1, Employee e2) { 
            Employee temp = e1;
            e1 = e2;
            e2 = temp;
        }
    
        /** * 雇员类 */
        static class Employee { 
            /** 姓名 */
            private String name;
    
            /** 薪水 */
            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;
            }
        }
    
    }

执行结果如下：

![在这里插入图片描述][951dcbf429dd46b29d536bfc60b59511.png]  
  由于java不是引用传递，所以上面的e1并不是employee1。  
  e1只是employee1 copy出来的一个引用，这两个引用指向同一个地址，但是这俩并不是一个引用。所以可以说e1和e2互换了引用地址，但是不能说employee1和employee2交换了地址。

下面是验证代码：

package com.demo.test.demo.api;
    
    /** * 探究Java究竟是值传递还是引用传递 * * @author zhao.hualuo * Create at 2021/8/9 */
    public class ParameterDemo { 
    
        public static void main(String[] args) { 
            Employee employee1 = new Employee("张三",1500);
            Employee employee2 = new Employee("李四",2000);
            System.out.printf("外面：employee1：%s,employee2：%s",employee1,employee2);
            System.out.println();
            swap(employee1, employee2);
            System.out.println();
            System.out.printf("外面：employee1：%s,employee2：%s",employee1,employee2);
        }
    
        public static void swap(Employee e1, Employee e2) { 
            System.out.printf("初始：e1：%s,e2：%s",e1,e2);
            Employee temp = e1;
            e1 = e2;
            e2 = temp;
            System.out.println();
            System.out.printf("最后：e1：%s,e2：%s",e1,e2);
        }
    
        /** * 雇员类 */
        static class Employee { 
            /** 姓名 */
            private String name;
    
            /** 薪水 */
            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;
            }
        }
    
    }

执行结果：  
![在这里插入图片描述][21069903311e4966936c99a33dccee40.png]

[951dcbf429dd46b29d536bfc60b59511.png]: /images/20220829/5ad8d439dba7478baa70f0e6dd566214.png
[21069903311e4966936c99a33dccee40.png]: /images/20220829/4a952751330443a1ad4861a4472c87eb.png