Java NullPointerException during read from keyboard -

-

i need read values keyboard table, , guess it's going out of range, can't figure out how fix it.

exception in thread "main" java.lang.nullpointerexception @ b12.app.main(app.java:36)

this line tab.matrix[ai][aj]=parser;

whole code:

import java.io.bufferedreader; import java.io.ioexception; import java.io.inputstreamreader;  class matrix{     public matrix() {      }     int rozmiar;     double matrix[][]; }  public class app {     public static void main(string[] args){         matrix tab = new matrix();         int parser;         bufferedreader br = new bufferedreader(new inputstreamreader(system.in) );         system.out.println("podaj rozmiar macierzy: ");             try {                 parser = integer.parseint(br.readline());                 tab.rozmiar = parser;             } catch (ioexception e) {                 // todo auto-generated catch block                 e.printstacktrace();             }               system.out.println("uzupelnij wiersze macierzy: ");                 for(int ai=1; ai<=tab.rozmiar; ai++){                     for(int aj=1; aj<=tab.rozmiar; aj++){                         bufferedreader zm = new bufferedreader(new inputstreamreader(system.in) );                             try {                                 parser = integer.parseint(zm.readline());                                 tab.matrix[ai][aj]=parser;                             } catch (ioexception e) {                                 // todo auto-generated catch block                                 e.printstacktrace();                             }                                    }                 }                 drukuj(tab);         }          static void drukuj(matrix m){             int ai,aj;             for(ai=1; ai>=m.rozmiar; ai++)             {                 for(aj=1; aj>=m.rozmiar; aj++)                 {                     if(ai==1){                     system.out.println("[" + m.matrix[ai][aj]);                     }                     if(ai!=1 && ai==m.rozmiar){                         system.out.println(" " + m.matrix[ai][aj] + " " );                     }                     else if(ai==m.rozmiar){                     system.out.println(m.matrix[ai][aj] + "]" );                     }                 }             }         }      public double det(matrix m){         double wynik = 0;          if(m.rozmiar==1){             wynik=m.matrix[1][1];         }         else if(m.rozmiar==2){             wynik=(m.matrix[1][1]*m.matrix[2][2])-(m.matrix[1][2]*m.matrix[2][1]);         }         else{             for(int n=1; n<m.rozmiar +1; n++){                 matrix tmpm = new matrix();                 tmpm.rozmiar=m.rozmiar - 1;                 int k=1,j;                 for(j=2; j<m.rozmiar; j++){                     for(k=1; k<m.rozmiar; k++){                         if(k>n) tmpm.matrix[j-1][k] = m.matrix[j][k];                         else if(k<n) tmpm.matrix[j-1][k-1] = m.matrix[j][k];                    }                 }                wynik+=m.matrix[1][n]*math.pow(-1, (j+k))*det(tmpm);                 }         }          return wynik;     } }

your array declared never instantiated. add line:

tab.matrix = new double[parser][parser];

after this:

tab.rozmiar = parser;

Comments

Post a Comment

Popular posts from this blog

android - Spacing between the stars of a rating bar? -

-
ho can set spacing beween stars? thats ratingbar: ratingbar = (ratingbar) inflater.inflate(r.layout.ratingbar, null); ratingbar.setlayoutparams(new layoutparams(layoutparams.wrap_content, layoutparams.wrap_content)); the layout: <?xml version="1.0" encoding="utf-8"?> <ratingbar xmlns:android="http://schemas.android.com/apk/res/android" style="@style/mystyle" android:layout_alignparentright="true" android:layout_height="19dp" android:layout_width="wrap_content" android:numstars="5"> </ratingbar> the style: <style name="mystyle" parent="@android:style/widget.ratingbar"> <item name="android:progressdrawable">@drawable/android_r2_ratingstar_yellow</item> <item name="android:indeterminatedrawable">@drawable/android_r2_ratingstar_grey</item> </style> thanks, cheers you have ...
Read more

html - Instapaper-like algorithm -

-
does of algorithm extracts contents webpage? instapaper ? there 2 steps instapaper does: find main content block on page (excluding headers, footers, menus etc) from content block extract , format text to find content block (typically html block element, div containing key page text content) instapaper uses algorithm 1 used readability . can @ source of readability.js see what's going on, @ core tries find area on page highest text/link ratio, although has other simple scoring metrics (e.g. off top of head, things ratio of text commas, para elements etc) go heuristics. once have identified root node element, relevant content, you'll need format it, if want can pull node element containing text out of source document , insert yours, in reality you'll want remove existing styles , apply own, standard , feel. if want output nice text-only can use jericho's renderer . update1 : should mention else instapaper - follow 'pagination' links (...
Read more

c# - How to execute a particular part of code asynchronously in a class -

-
i creating speech recognition engine that's going respond user commands.i have created button enable , disable speech recognition per user convenience.i have used dispose() of speech engine disable speech recoginition.here code private void button1_click(object sender, routedeventargs e) { engineon = !engineon; if (engineon) { speechengine = speech.createspeechengine(); //speech class creates , returns new speech engine. speechengine.audiolevelupdated += new eventhandler<audiolevelupdatedeventargs>(speechengine_audiolevelupdated); // use system's default microphone speechengine.setinputtodefaultaudiodevice(); speechengine.loadgrammar(new dictationgrammar()); // start listening speechengine.recognizeasync(recognizemode.multiple); } else { speechclass.myengine.dispose(); } } but disposal of speech obj...
Read more