4.5 方法参数

书中提到:

• Java 程序设计语言总是采用按值调用

基本类型:

引用类型:

这种行为与 Go 类似. 主要要区分基本类型和引用类型.

书中举了例子来说明常见的错误: Java 方法参数是引用类型

• 方法内部的交换对外层不起作用

自己写的测试用例:

package chapter04;
import java.time.LocalDate;
import java.util.Objects;
public class Employee {
    private String name;
    private double salary;
    private LocalDate hireDay;
    public Employee(String n, double s, int year, int month, int day) {
        name = Objects.requireNonNull(n, "The name cannot be null");
        salary = s;
        hireDay = LocalDate.of(year, month, day);
    }
    public String getName() {
        return name;
    }
    public static void Exchange(Employee x, Employee y) {
        Employee tmp = x;
        x = y;
        y = tmp;
    }
}
public class Main {
    public static void main(String[] args) {
        Employee employee1 = new Employee("abc", 123.03, 2021, 4, 28);
        Employee employee2 = new Employee("def", 123.03, 2021, 4, 28);
        Employee.Exchange(employee1, employee2);
        System.out.println(employee1.getName()); // abc
        System.out.println(employee2.getName()); // def
    }
}

如果非要实现对外层进行交换, 那么参数的类型应该是 指针的指针,