CODEWITHSUNDEEP
javaarrays
Demostroyer
Demostroyer

Reputation: 73

Reason for it telling me NullPointerexception

Why is this giving me the error of Nullpointerexception? It is happening on the 3rd line of my code, so my first for loop. Just so you know, this is a method with access to other parts of a larger code. 

public static void insertionsort() 
{
    for (int outer = 1; outer < array.length; outer++)//Outer=next number to be sorted 
    { 
        String temp = array[outer]; //Stores it for later use
        int inner = outer; // inner used to track shifts 
        while (inner > 0 && array[inner - 1].compareTo(temp) >= 0) 
        {  
            array[inner] = array[inner - 1];//Swaps the number
            inner--;// Decrements
        } //shift them all right until one is smaller 
        array[inner] = temp;//Now it will put the stored number into its ordered position. 
    }
}

Upvotes: 0

Views: 72

Answers (2)

ebrito
ebrito

Reputation: 1

I just created a unit test to reproduce the NPE, and I didn't get any error. My suggestion is to split the for sentece in multiple lines, so you will get exactly where is the NPE. 

    for (int outer = 1; 
            outer < array.length; 
            outer++)//Outer=next number to be sorted 
    {

The full unit test is:

package src.test.java;  
import org.junit.Test;

public class TestOne {


   private static String[] array={"sa","se","si","so", "su"};
   @Test
   public void TestOne(){
    this.insertionsort();
   }

   public static void insertionsort() 
   {
    for (int outer = 1; 
            outer < array.length; 
            outer++)//Outer=next number to be sorted 
    { 
        String temp = array[outer]; //Stores it for later use
        int inner = outer; // inner used to track shifts 
        while (inner > 0 && array[inner - 1].compareTo(temp) >= 0) 
        {  
            array[inner] = array[inner - 1];//Swaps the number
            inner--;// Decrements
        } //shift them all right until one is smaller 
        array[inner] = temp;//Now it will put the stored number into its ordered position. 
    }
}

}

Upvotes: 0

Ankit Rustagi
Ankit Rustagi

Reputation: 5637

The variable array is not defined in this line

for (int outer = 1; outer < array.length; outer++)//Outer=next number to be sorted

If this is a function parameter then add it like this

public static void insertionsort(int[] array) 
{
     for (int outer = 1; outer < array.length; outer++)//Outer=next number to be sorted

or define it inside

public static void insertionsort() 
{

    int[] array = {2,1,4,7,6,3};

    for (int outer = 1; outer < array.length; outer++)//Outer=next number to be sorted

Upvotes: 2

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