pta_java根据已有类Worker，使用LinkedList编写一个WorkerList类，实现计算所有工人总工资的功能。 (10分)

Main类：在main方法中，调用constructWorkerList方法构建一个Worker对象链表，调用computeTotalSalary方法计算总工资并输出到屏幕。

根据要求，编写WorkerList类的构造方法和方法。编程要求如下：

数据使用Scanner对象从键盘读入；
constructWorkerList方法：从键盘读入工人数量workerNum，调用readInWorker方法读入workerNum个工人，将每个工人对象添加到链表中，最后返回链表。
readInWorker方法：使用scanner从键盘读入一个工人的姓名、年龄和工资，构建一个Worker对象并返回
computeTotalSalary方法：计算链表中所有工人的工资总和并返回。

提示： Scanner对象读入字符串的方法：

next()方法读入一个字符串，读到空白符结束；(本题中使用next()方法读入字符串)

nextLine()也是读入一个字符串，但读取到回车(也就是"\r")结束。
函数接口定义：

Worker readInWorker();
List<Worker> constructWorkerList();
double computeTotalSalary(List<Worker> list);

import java.util.*;

public class Main {
    public static void main(String[] args) {        
        WorkerList app=new WorkerList();                        
        List<Worker> list=app.constructWorkerList();        
        System.out.println(app.computeTotalSalary(list));    
    }
}

/* 请在这里填写答案：将WorkerList类补充在这里 */


class Worker {    
    private String name;
    private double salary;

    public Worker() { }

    public Worker(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;
    }

    public String toString() {
        return name + " "+salary;
    }    
}

class WorkerList//法一
{
	public List<Worker> constructWorkerList(){
		Scanner sc = new Scanner(System.in);		
		List<Worker> list=new LinkedList<Worker>();
		int NUM = sc.nextInt();
		for (int i = 0; i < NUM; i++) {
			Worker worker = new Worker(sc.next(),sc.nextDouble());
			list.add(worker);
		}
		sc.close();
		return list;
	}
	public double computeTotalSalary(List<Worker> list) {
		double sum = 0; 
		for(Worker obj: list)
		{
			sum += obj.getSalary();
		}
		return sum;
	}
}

class WorkerList//法二
{
	public List<Worker> constructWorkerList(){
        Scanner sc = new Scanner(System.in);
        List<Worker> list=new ArrayList<>();
        int NUM = sc.nextInt();
        for (int i = 0; i < NUM; i++) {
            list.add(readInWorker(sc));
        }
        sc.close();
        return list;
    }
    public Worker readInWorker(Scanner sc) {
        return new Worker(sc.next(),sc.nextDouble());
    }
    public double computeTotalSalary(List<Worker> list) {
		double sum = 0; 
		for(Worker obj: list)
		{
			sum += obj.getSalary();
		}
		return sum;
	}
}

class WorkerList//法三
{
	private Scanner sc;//Scanner不要有多个
	public List<Worker> constructWorkerList(){
		sc = new Scanner(System.in);		
		List<Worker> list=new ArrayList<Worker>();
		int NUM = sc.nextInt();
		for (int i = 0; i < NUM; i++) {
			list.add(readInWorker());
		}
		sc.close();
		return list;
	}
	public Worker readInWorker() {
		Worker worker = new Worker(sc.next(),sc.nextDouble());
		//sc.close();//这里不能有!!
		return worker;			
	}
	public double computeTotalSalary(List<Worker> list) {
		double sum = 0; 
		for(Worker obj: list)
		{
			sum += obj.getSalary();
		}
		return sum;
	}
}