如何在java中解决NullPointerException？ [英] How to solve NullPointerException in java?

问题描述

这个简单的程序在行{System.out.println（Id =+ staffs [j] .getId（））;}中显示NullPointerException，我该如何解决这个问题？



谢谢

This simple programs shows NullPointerException in line { System.out.println("Id = " + staffs[j].getId());}, how can i solve this issue?

Thanks

import java.util.Scanner;
import java.util.Arrays;
public class Main {

	public static void main(String[] args) {
		int ID;
		String Name;
		String LastName;
		String FatherName;
		int Salary;
		String Position;

		String input;

		boolean repeat = true;

		Scanner scan = new Scanner(System.in);
		
		Staff[] staffs = new Staff[100];
		int i = 0;
		while (repeat) {

			String userInput;
			System.out.println("Please Enter Staff Information!");

			System.out.println("ID: ");
			ID = scan.nextInt();

			System.out.println("Name: ");
			Name = scan.next();

			System.out.println("Last Name: ");
			LastName = scan.next();

			System.out.println("Father Name: ");
			FatherName = scan.next();

			System.out.println("Salary : ");
			Salary = scan.nextInt();

			System.out.println("Position: ");
			Position = scan.next();

			scan.nextLine();

			System.out
					.println("Type 'yes' or 'no' if you want to continure or not ");
			input = scan.nextLine();

			if ("yes".equals(input))
				repeat = true;
			else
				repeat = false;

			staffs[i++] = new Staff(ID, Name, LastName, FatherName, Salary,Position);

		}
		System.out.println("Thank you!");
		
		for (int j = 0; j < staffs.length - 1; j++) {
			System.out.println("Id = " + staffs[j].getId());
			System.out.println("Name = " + staffs[j].getName());
			System.out.println("LastName = " + staffs[j].getLastName());
			System.out.println("FatherName = " + staffs[j].getFatherName());
			System.out.println("Salary = " + staffs[j].getSalary());
			System.out.println("Position = " + staffs[j].getPosition());
		
		}
		}
	}

public class Staff {
	
	public int ID;
	public  String Name;
	public String LastName;
	public	 String FatherName;
	public  int Salary;
	public  String Position;
	
	public Staff(int ID, String Name, String LastName, String FatherName, int Salary, String Position){
		
		this.ID = ID;
		this.Name = Name;
		this.LastName = LastName;
		this.FatherName = FatherName;
		this.Salary = Salary;
		this.Position = Position;
		}
			public  int getId(){
				return ID;
			}
			public String getName(){
				 return Name;
				 }
			 public String getLastName(){
				 return LastName;
			 }
			 public String	getFatherName(){
				 return FatherName;
			 }
			 public int getSalary(){
				 return Salary;
				 }
			 public String getPosition(){
				 return Position;
				 }
	}

推荐答案

虽然我没有测试过代码但它应该给你提示移动on。

Though I have not tested the code but it should give you the hint to move on.

import java.util.Scanner;
import java.util.Arrays;
import java.util.ArrayList;

public class Main {
 
	public static void main(String[] args) {
		int ID;
		String Name;
		String LastName;
		String FatherName;
		int Salary;
		String Position;
 
		String input;
 
		boolean repeat = true;
 
		Scanner scan = new Scanner(System.in);
		
		ArrayList ArrayList<staff> staffList= new ArrayList<staff>();
		
		int i = 0;
		while (repeat) {
 
			String userInput;
			System.out.println("Please Enter Staff Information!");
 
			System.out.println("ID: ");
			ID = scan.nextInt();
 
			System.out.println("Name: ");
			Name = scan.next();
 
			System.out.println("Last Name: ");
			LastName = scan.next();
 
			System.out.println("Father Name: ");
			FatherName = scan.next();
 
			System.out.println("Salary : ");
			Salary = scan.nextInt();
 
			System.out.println("Position: ");
			Position = scan.next();
 
			scan.nextLine();
 
			System.out
					.println("Type 'yes' or 'no' if you want to continure or not ");
			input = scan.nextLine();
 
			if ("yes".equals(input))
				repeat = true;
			else
				repeat = false;
 
			Staff tmpStaff = new Staff(ID, Name, LastName, FatherName, Salary,Position);
			staffList.add(tmpStaff);
 
		}
		System.out.println("Thank you!");
		
		for (Staff tmpStaff : staffList) {
			System.out.println("Id = " + tmpStaff.getId());
			System.out.println("Name = " + tmpStaff.getName());
			System.out.println("LastName = " + tmpStaff.getLastName());
			System.out.println("FatherName = " + tmpStaff.getFatherName());
			System.out.println("Salary = " + tmpStaff.getSalary());
			System.out.println("Position = " + tmpStaff.getPosition());
		
		}
		}
	}</staff></staff>

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