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Thread: How can i fix my null pointer exception error?

  1. #1
    Junior Member
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    Unhappy How can i fix my null pointer exception error?

    This is my entire code.. what i do keep getting nullpointerexception error whenever i input 1 or 2 whenever the code is asking me to input the type of display to be shown..

    this is my error - "Exception in thread "main" java.lang.NullPointerException
    at dakilangtaoako.DakilangTaoAko.alphabetSorter(Dakil angTaoAko.java:195)
    at dakilangtaoako.DakilangTaoAko.main(DakilangTaoAko. java:91)
    Java Result: 1 "

    package dakilangtaoako;
    import java.io.BufferedReader;
    import java.io.IOException;
    import java.io.InputStreamReader;
    import java.util.logging.Level;
    import java.util.logging.Logger;


    public class DakilangTaoAko {
    public static void main(String[] args){

    BufferedReader dataIn = new BufferedReader(new InputStreamReader( System.in) );
    String mydata[][] = new String[5][3] ;
    String inttoword [] = new String [5];
    int wordtoint[] = new int [5];
    int mychoice = 0;
    String toreturn = "";

    for (int outside = 0; outside < 5; outside++){
    System.out.println("Entry no." + (outside + 1));
    for (int inside = 0; inside < 3; inside++){
    if(inside == 0){
    try {
    System.out.print("Name: ");
    mydata[outside][inside]= dataIn.readLine();
    } catch (IOException ex) {
    Logger.getLogger(DakilangTaoAko.class.getName()).l og(Level.parse("OK"), null, ex);
    }
    }
    else if(inside == 1){
    try {
    System.out.print("ID: ");
    mydata[outside][inside]= dataIn.readLine();
    } catch (IOException ex) {
    Logger.getLogger(DakilangTaoAko.class.getName()).l og(Level.parse("OK"), null, ex);
    }
    }
    else if(inside ==2){
    try {
    System.out.print("Subject: ");
    mydata[outside][inside]= dataIn.readLine();
    } catch (IOException ex) {
    Logger.getLogger(DakilangTaoAko.class.getName()).l og(Level.parse("OK"), null, ex);
    }


    }
    }
    }
    for(int outside= 0; outside <5; outside++){
    for(int inside = 1; inside <= 3; inside++){
    if(inside ==0)
    inttoword[outside]=(mydata[outside][inside])+";"+(mydata[outside][inside]);
    }
    }
    for(int outside = 0; outside < 5; outside++){
    for(int inside = 1; inside <= 3; inside++){
    if(inside ==0)
    wordtoint[outside]=Integer.parseInt(mydata[outside][inside]);
    }
    }


    for(int i=0;i<5;i++){
    wordtoint[i]=Integer.parseInt(mydata[i][1]);
    }

    while(mychoice != 5){
    System.out.println("-------- DISPLAY OPTIONS --------");
    System.out.println("\t [1] Display Entries Alphabetically ");
    System.out.println("\t [2] Display Entries by Ascending ID number ");
    System.out.println("\t [3] Display Students Enrolled in Prog2 ");
    System.out.println("\t [4] Display Students Enrolled in CSO ");
    System.out.println("\t [5] Exit ");
    System.out.println();
    System.out.print("\t Choice:");
    try {
    mychoice = Integer.parseInt(dataIn.readLine());
    } catch (IOException ex) {
    Logger.getLogger(DakilangTaoAko.class.getName()).l og(Level.SEVERE, null, ex);
    }

    switch (mychoice){



    case 1:
    System.out.println("----Entries In Alphabetical Order----");
    alphabetSorter(inttoword);
    for(int limiter = 0; limiter < 5; limiter++)
    System.out.println(inttoword[limiter]);


    System.out.print("Press [r] to Return to Main Menu...");
    try {
    toreturn = dataIn.readLine();
    } catch (IOException ex) {
    Logger.getLogger(DakilangTaoAko.class.getName()).l og(Level.SEVERE, null, ex);
    }
    if("r".equals(toreturn))
    break;
    case 2:

    System.out.println(" ---- Entries by Ascending ID Number ----");
    for(int outside = 0; outside < 5; outside++){
    numSorter(wordtoint);
    for(int inside = 0; inside < 5; inside++){
    if(Integer.parseInt(mydata[inside][1])== wordtoint[outside])
    System.out.println(wordtoint[outside] + ";" + mydata[inside][0]);
    }
    }
    System.out.print("Press [r] to return to main Menu...");
    try {
    toreturn = dataIn.readLine();
    } catch (IOException ex) {
    Logger.getLogger(DakilangTaoAko.class.getName()).l og(Level.SEVERE, null, ex);
    }
    if("r".equals(toreturn))
    break;

    case 3:
    System.out.println(" ---- Students Enrolled in Prog2 ----");
    String mustfind1 = "PROG2";
    for(int outside = 0; outside < 5; outside++){
    if(mydata[outside][2].equalsIgnoreCase(mustfind1)){
    System.out.println(mydata[outside][0]+";"+mydata[outside][1]);
    }
    }System.out.print("Press [r] to Return to Main Menu...");
    try {
    toreturn = dataIn.readLine();
    } catch (IOException ex) {
    Logger.getLogger(DakilangTaoAko.class.getName()).l og(Level.SEVERE, null, ex);
    }
    if("r".equals(toreturn))
    break;

    case 4:
    System.out.println(" ---- Students Enrolled in CSO ---- ");
    String mustfind2 = "CSO";
    for(int outside = 0; outside < 5; outside++){
    if(mydata[outside][2].equalsIgnoreCase(mustfind2))
    System.out.println(mydata[outside][0]+";"+mydata[outside][1]);
    }
    System.out.print("Press [r] to Return to Main Menu...");
    try {
    toreturn = dataIn.readLine();
    } catch (IOException ex) {
    Logger.getLogger(DakilangTaoAko.class.getName()).l og(Level.SEVERE, null, ex);
    }
    if("r".equals(toreturn))
    break;

    case 5:
    mychoice = 5;

    break;

    default:
    System.out.println("Sorry the Number is Not in the Choices!!");
    System.out.print("Press [r] to Return to Main Menu...");
    try {
    toreturn = dataIn.readLine();
    } catch (IOException ex) {
    Logger.getLogger(DakilangTaoAko.class.getName()).l og(Level.SEVERE, null, ex);
    }
    if("r".equals(toreturn))
    break;
    } }
    }
    public static void numSorter(int given[]){

    int temp;
    for(int outside = 0; outside < given.length-1; outside++)
    {
    for(int inside = outside+1 ; inside < given.length; inside++)
    {
    if(given[outside] > given[inside])
    {
    temp = given[outside];
    given[outside]= given[inside];
    given[inside]=temp;
    }
    }
    }
    }
    public static void alphabetSorter(String given[]){

    String temp;
    for(int outside = 0; outside < given.length -1; outside++)
    {
    for(int inside = outside +1; inside < given.length; inside++)
    {
    if(given[outside].compareToIgnoreCase(given[inside])>0)
    {
    temp= given[outside];
    given[outside]= given[inside];
    given[inside]=temp;
    }
    }
    }
    }

    }


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: How can i fix my null pointer exception error?

    his is my error - "Exception in thread "main" java.lang.NullPointerException
    at dakilangtaoako.DakilangTaoAko.alphabetSorter(Dakil angTaoAko.java:195)
    Look at line 195 and find the variable with the null value. Then backtrack in the code to find why that variable does not have a valid value.

    Please edit your post and wrap your code with code tags:
    [code=java]
    YOUR CODE HERE
    [/code]
    to get highlighting and preserve formatting.
    If you don't understand my answer, don't ignore it, ask a question.

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