我不能讓我的程序進行測試：「顯示java.lang.NullPointerException」

Question

當我嘗試和運行程序這是計算機將返回：

LAST_NAMEFIRST_NAME您好Test1的的Test2 Test3的TEST4 TEST5平均

級

線程「main」中的異常java.lang.NullPointerException在 tests.Tests.main（Tests.java:132）C：\ Users \ Michael Jr \ AppData \ Local \ NetBeans \ Cache \ 8.1 \ executor-snippets \ run.xml：53：Java 返回：1 BUILD FAILED（總時間：0秒）

package tests; 
import java.io.BufferedReader; 
import java.io.FileReader; 
import java.io.IOException; 
import java.text.DecimalFormat; 
import java.util.ArrayList; 
import java.util.List; 
/** 
* 
* @author Michael 
*/ 
public class Tests { 

    private String fname; 
    private String lname; 
    private int[] scores; 

    public Tests(String entry) 
    { 
     String[] data=entry.split(" "); 
     scores=new int[data.length-2]; 
     this.setFname(data[0]); 
     this.setLname(data[1]); 
     for(int i=2;i<data.length;i++) 
     { 
      scores[i-2]=Integer.parseInt(data[i]); 
     } 
    } 
    public int[] getScores() { 
     return scores; 
    } 
    public void setScores(int[] scores) { 
     this.scores = scores; 
    } 

    public static String getAverageScore(int[] a) 
    { 
     int sum=0; 
     for(int e:a) 
     { 
      sum+=e; 
     } 
     return new DecimalFormat("##.##").format((double)sum/(double)a.length); 
    } 

    public static void showAverage(List<Tests> e) 
    { 
     for(Tests s:e) 
     { 
      System.out.println(s); 
     } 
    } 
    public String getGrade() 
    { 
     double d=Double.parseDouble(Tests.getAverageScore(scores)); 
     if(d<=100 && d>=90) 
     { 
      return "A"; 
     } 
     else if(d<90 && d>=80) 
     { 
      return "B"; 
     } 
     else if(d<80 && d>=70) 
     { 
      return "C"; 
     } 
     else if(d<70 && d>=60) 
     { 
      return "D"; 
     } 
     else 
     { 
      return "F"; 
     } 
    } 
    public String getFname() { 
     return fname; 
    } 
    public void setFname(String fname) { 
     this.fname = fname; 
    } 
    public String getLname() { 
     return lname; 
    } 
    public void setLname(String lname) { 
     this.lname = lname; 
    } 
    public String toString() 
    { 
     return getFname()+"\t\t"+getLname()+"\t\t"+scores[0]+"\t\t"+scores[1]+"\t\t"+scores[2]+"\t\t"+scores[3]+"\t\t"+scores[4]+"\t\t"+getAverageScore(scores)+"\t\t"+getGrade(); 
    } 

    public static ArrayList<Tests> read(String path) 
    { 
     BufferedReader br = null; 
     try { 

      String sCurrentLine; 
      ArrayList<Tests> ar=new ArrayList<Tests>(); 
      br = new BufferedReader(new FileReader("C:\\Users\\Michael Jr\\Desktop\\ch9_Ex13Data.txt")); 

      while ((sCurrentLine = br.readLine()) != null) 
      { 
       ar.add(new Tests(sCurrentLine)); 
      } 
      return ar; 

     } 
     catch (Exception e) 
     { 

     } 
     finally { 
      try { 
       if (br != null)br.close(); 
      } catch (IOException ex) { 
       ex.printStackTrace(); 
      } 
     } 
     return null; 
    } 
    public static void main(String[] a) 
    { 
     ArrayList<Tests> ar=read("E:/score.txt"); 
     System.out.println("First_Name\tLast_Name\tTest1\t\tTest2\t\tTest3\t\tTest4\t\tTest5\t\tAverage\t\tGrade"); 
     for(Tests e:ar) 
     { 
      System.out.println(e); 
     } 
    } 
} 

Answer 1

您應該檢查你的閱讀功能的結果：

public static void main(String[] a) 
    { 
     ArrayList<Tests> ar=read("E:/score.txt"); 
     if (ar != null){ 
      System.out.println("First_Name\tLast_Name\tTest1\t\tTest2\t\tTest3\t\tTest4 \t\tTest5\t\tAverage\t\tGrade"); 
      for(Tests e:ar) 
      { 
       System.out.println(e); 
      } 
     } else { 
      System.out.println("Could not read file"); 
     } 
    } 

Answer 2

你驗證try聲明？讀函數返回「空」的值。我認爲這個問題是當你閱讀文件時。

String sCurrentLine; 
     ArrayList<Tests> ar=new ArrayList<Tests>(); 
     br = new BufferedReader(new FileReader("C:\\Users\\Michael Jr\\Desktop\\ch9_Ex13Data.txt")); 

     while ((sCurrentLine = br.readLine()) != null) 
     { 
      ar.add(new Tests(sCurrentLine)); 
     } 
     return ar; 

如果您能夠共享文件，我將驗證此代碼是否正確！