Java 存储员工信息：数组、集合和 Map 三种方法

本文将介绍使用 Java 存储多个员工信息（包括工号、姓名、年龄和入职时间）的三种方法：数组、集合和 Map。并提供示例代码，演示如何打印所有员工姓名以及输出员工总数。

方式一：使用数组存储员工信息

public class Employee {
    private int id;
    private String name;
    private int age;
    private Date hireDate;

    public Employee(int id, String name, int age, Date hireDate) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.hireDate = hireDate;
    }

    public String getName() {
        return name;
    }
}

public class Main {
    public static void main(String[] args) {
        Employee[] employees = new Employee[3];
        employees[0] = new Employee(1, '张三', 22, new Date());
        employees[1] = new Employee(2, '李四', 25, new Date());
        employees[2] = new Employee(3, '王五', 28, new Date());

        System.out.println('员工姓名：');
        for (Employee employee : employees) {
            System.out.println(employee.getName());
        }
        System.out.println('员工个数：' + employees.length);
    }
}

方式二：使用集合存储员工信息

public class Employee {
    private int id;
    private String name;
    private int age;
    private Date hireDate;

    public Employee(int id, String name, int age, Date hireDate) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.hireDate = hireDate;
    }

    public String getName() {
        return name;
    }
}

public class Main {
    public static void main(String[] args) {
        List<Employee> employees = new ArrayList<>();
        employees.add(new Employee(1, '张三', 22, new Date()));
        employees.add(new Employee(2, '李四', 25, new Date()));
        employees.add(new Employee(3, '王五', 28, new Date()));

        System.out.println('员工姓名：');
        for (Employee employee : employees) {
            System.out.println(employee.getName());
        }
        System.out.println('员工个数：' + employees.size());
    }
}

方式三：使用 Map 存储员工信息

public class Employee {
    private int id;
    private String name;
    private int age;
    private Date hireDate;

    public Employee(int id, String name, int age, Date hireDate) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.hireDate = hireDate;
    }

    public String getName() {
        return name;
    }
}

public class Main {
    public static void main(String[] args) {
        Map<Integer, Employee> employeeMap = new HashMap<>();
        employeeMap.put(1, new Employee(1, '张三', 22, new Date()));
        employeeMap.put(2, new Employee(2, '李四', 25, new Date()));
        employeeMap.put(3, new Employee(3, '王五', 28, new Date()));

        System.out.println('员工姓名：');
        for (Employee employee : employeeMap.values()) {
            System.out.println(employee.getName());
        }
        System.out.println('员工个数：' + employeeMap.size());
    }
}

这三种方法各有优劣：

数组适合存储固定数量的员工信息，且访问速度较快；
集合可以存储任意数量的员工信息，方便添加和删除元素；
Map 可以根据员工的工号快速访问员工信息。

选择哪种存储方式取决于具体的需求。