CODEWITHSUNDEEP
javastringnullpointerexceptioncompareto
user3633233
user3633233

Reputation: 5

Can't get Strings compareTo method to work

for some reason I can't get Strings compareTo method to work. I get this error message: 

exception in thread main java.lang.NullpointerException
at java.lang.String.compareTo(Unknown Source)
at Sort.main(Sort.java:27)

What can I do to fix this? (this code demands that the to arrays are allready sorted individually.)

import java.util.*;

class Sort{
    public static void main(String[] args){
        String[] ord = new String[6];
        ord[0] = "astra";
        ord[1] = "bilum";
        ord[2] = "deliber";
        ord[3] = "kaliber";
        ord[4] = "suppe";
        ord[5] = "vorte";

        String[] ordet = new String[6];
        ord[0] = "akilles";
        ord[1] = "kopper";
        ord[2] = "lipton";
        ord[3] = "mus";
        ord[4] = "orkester";
        ord[5] = "toving";

        String[] flettet = new String[ord.length + ordet.length];

        for(int i = 0; i < ord.length; i++){
            int teller = i; 
            for(int j = 0; j < ordet.length; j++){
                if(ord[i].compareTo(ordet[j]) > 0){ //line 27
                    teller += 1;
                }
            }
            flettet[teller] = ord[i];
        }
    }   
}

Upvotes: 0

Views: 830

Answers (3)

DirkyJerky
DirkyJerky

Reputation: 1168

String[] ordet = new String[6]; ord[0] = "akilles"; ord[1] = "kopper"; ord[2] = "lipton"; ord[3] = "mus"; ord[4] = "orkester"; ord[5] = "toving"; You never filled the ordet array, you just over-wrote the ord array. At this point there is no elements in the ordet array, just nulls.

So...

if(ord[i].compareTo(ordet[j]) > 0){ //line 27 is comparing to an element that doesnt exist, and #compareTo throws a NullPointerException because you passed in a null, not a String

Upvotes: 0

Aries7
Aries7

Reputation: 46

You never assign any values to ordet. so compareTo is comparing a string to NULL

    String[] ord = new String[6];
    ord[0] = "astra";
    ord[1] = "bilum";
    ord[2] = "deliber";
    ord[3] = "kaliber";
    ord[4] = "suppe";
    ord[5] = "vorte";

    String[] ordet = new String[6];
    ord[0] = "akilles";                //overwriting ord[0]
    ord[1] = "kopper";                 //overwriting ord[1]
    ord[2] = "lipton";                 //overwriting ord[2]
    ord[3] = "mus";                    //overwriting ord[3]
    ord[4] = "orkester";               //overwriting ord[4]
    ord[5] = "toving";                 //overwriting ord[5]

Upvotes: 0

Rob
Rob

Reputation: 3381

Do you mean - it looks like you are setting the wrong array:

    String[] ordet = new String[6];
    ordet[0] = "akilles";
    ordet[1] = "kopper";
    ordet[2] = "lipton";
    ordet[3] = "mus";
    ordet[4] = "orkester";
    ordet[5] = "toving";

Upvotes: 5

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