Java 员工信息存储与输出：数组、列表、映射和集合

Java 员工信息存储与输出：数组、列表、映射和集合

本文将演示使用 Java 四种方式存储员工信息（包括工号、姓名、年龄、入职时间），并打印所有员工姓名以及员工数量。这四种方式分别是：

1. 数组

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

    public Employee(int id, String name, int age, LocalDate 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, 'John', 25, LocalDate.of(2020, 1, 1));
        employees[1] = new Employee(2, 'Mary', 30, LocalDate.of(2015, 1, 1));
        employees[2] = new Employee(3, 'Tom', 35, LocalDate.of(2010, 1, 1));

        int count = employees.length;
        System.out.println('Total employees: ' + count);

        for (Employee employee : employees) {
            System.out.println(employee.getName());
        }
    }
}

2. 列表

import java.util.ArrayList;
import java.util.List;

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

    public Employee(int id, String name, int age, LocalDate 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, 'John', 25, LocalDate.of(2020, 1, 1)));
        employees.add(new Employee(2, 'Mary', 30, LocalDate.of(2015, 1, 1)));
        employees.add(new Employee(3, 'Tom', 35, LocalDate.of(2010, 1, 1)));

        int count = employees.size();
        System.out.println('Total employees: ' + count);

        for (Employee employee : employees) {
            System.out.println(employee.getName());
        }
    }
}

3. 映射

import java.util.HashMap;
import java.util.Map;

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

    public Employee(int id, String name, int age, LocalDate 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> employees = new HashMap<>();
        employees.put(1, new Employee(1, 'John', 25, LocalDate.of(2020, 1, 1)));
        employees.put(2, new Employee(2, 'Mary', 30, LocalDate.of(2015, 1, 1)));
        employees.put(3, new Employee(3, 'Tom', 35, LocalDate.of(2010, 1, 1)));

        int count = employees.size();
        System.out.println('Total employees: ' + count);

        for (Employee employee : employees.values()) {
            System.out.println(employee.getName());
        }
    }
}

4. 集合

import java.util.HashSet;
import java.util.Set;

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

    public Employee(int id, String name, int age, LocalDate 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) {
        Set<Employee> employees = new HashSet<>();
        employees.add(new Employee(1, 'John', 25, LocalDate.of(2020, 1, 1)));
        employees.add(new Employee(2, 'Mary', 30, LocalDate.of(2015, 1, 1)));
        employees.add(new Employee(3, 'Tom', 35, LocalDate.of(2010, 1, 1)));

        int count = employees.size();
        System.out.println('Total employees: ' + count);

        for (Employee employee : employees) {
            System.out.println(employee.getName());
        }
    }
}

本文中的代码示例展示了如何使用不同数据结构存储和访问员工信息，您可以根据实际需求选择最合适的方式。例如，如果您需要根据员工 ID 快速访问员工信息，则可以使用映射；如果您需要保证员工信息不重复，则可以使用集合。

希望本文对您有所帮助！