数组输出 - 删除null

Question

我计划打印一条消息，以显示数组中的数据结果。它假设看起来像 "7 *******"但我得到了"7 null*******"。

我想摆脱“null”

import java.util.ArrayList;    

public class FavorGameDisplay
{
private ArrayList<String> votedGame;
private String[] asterisk;
private int[] gameCount;


/**
 * Constructor for objects of class FavorGameDisplay
 */
public FavorGameDisplay()
{
    FavorGameData data = new FavorGameData();
    votedGame = data.getData();
    analyzeData();
}

/**
 * Analyze and recording counts of the following video games:
 * gameCount[0]: Nier: Automata
 * gameCount[1]: PlayerUnknown’s Battlegrounds
 * gameCount[2]: Wolfenstein 2: The New Colossus
 * gameCount[3]: Cuphead
 * gameCount[4]: any other video games
 */
private void analyzeData()
{
    gameCount = new int[5];
    asterisk = new String[5];
    for (String game : votedGame) 
    {
        if (game.equals("Nier: Automata")) 
        {
            gameCount[0]++;
            asterisk[0] += "*";
        }

        else if (game.equals("PlayerUnknown’s Battlegrounds")) 
        {
            gameCount[1]++;
            asterisk[1] += "*";
        }

        else if (game.equals("Wolfenstein 2: The New Colossus")) 
        {
            gameCount[2]++;
            asterisk[2] += "*";
        }           


        else if (game.equals("Cuphead")) 
        {
            gameCount[3]++;
            asterisk[3] += "*";
        }
        else
        {
            gameCount[4]++;
            asterisk[4] += "*";
        }
    }           
}





/**
 * Display the analyzed data as a histogram
 */
public void displayData()
{

    System.out.println("------------------------------------------");
    System.out.println("Number of people vote for each game: ");        
    System.out.println("Nier: Automata:   " + gameCount[0] + " " + asterisk[0]);
    System.out.println("PlayerUnknown’s Battlegrounds:  " + gameCount[1] + " " + asterisk[1]);
    System.out.println("Wolfenstein 2: The New Colossus:    " + gameCount[2] + " " + asterisk[2]);         
    System.out.println("Cuphead: " + gameCount[3] + " " + asterisk[3]);  
    System.out.println("Others: " + gameCount[4] + " " + asterisk[4]);  
    System.out.println("------------------------------------------");
}
}

Answer 1

您不首先初始化asterisk的元素;所以当你写：

asterisk[0] += "*";

您将其当前值（null）的字符串表示与"*"连接起来，因此最终得到null*。

在循环之前用空字符串填充数组：

Arrays.fill(asterisk, "");