assign a new value at a String array position in java

Question

Please find my example code below:

    String[] tempCrfFC = crfFC;                //crfFC is a String[] itself
    for(int i = 0; i < crfFC.length; i++) {
        String[] crfTok = tempCrfFC[i].split("\\s");
        if(crfTok.length == 40) {
            if(crfTok[39].split("/")[0].equals("O")) {
                Double v = Double.parseDouble(crfTok[39].split("/")[1]);
                if (v <= d && (i == 0 || prevTagged != i-1)) {
                    tempCrfFC[i].split("\\s")[39] = "A";    //<-------
                    System.out.println("val: "+tempCrfFC[i].split("\\s")[39]);
                    System.out.println("tempCrfFC: "+tempCrfFC[i]);
                    prevTagged = i;
                }
             }
        }
    }

Example of a tempCrfFC line:

The  T       Th      The     null    e       he      The     null   Aaa     Aa    1       1       1       0       0       0       0       0       0       0       0       0       0       0       0       0       0       0       0       O       B       O       B       O       0       DT      O       O/0.892667

At the line marked with "<-----" I wish to reassign the existing value to a new value "A". However, on printing the output, the observation is that the value at that index (39) remains unchanged. Could someone help me resolve this?

Thank you.

What a mess... Sorry to say that, but I can't help it. First off: Clean up you variable names! A few extra characters won't bust your harddrive. — nfechner
– nfechner, Commented Jan 2, 2012 at 18:09
I see a lot of unnececarly code. Just verify everything upto the "<-----" works yourself, and let us look at the "<-----" line only. You will need something like tempCrfFC[i] = tempCrfFC[i].substring(0,38) + "A" + tempCrfFC[i].substring(40,tempCrfFC[i].length()) — Dorus
– Dorus, Commented Jan 2, 2012 at 18:12
For example: Expand v to currentValue. Rename d to whatever it actually stands for. — nfechner
– nfechner, Commented Jan 2, 2012 at 18:13
@rookie: crfFC and crfTok means nothing to anyone who isn't you. You aren't limited to 5 character, so make variable names meaningful. — unholysampler
– unholysampler, Commented Jan 2, 2012 at 18:14

Bhesh Gurung · Accepted Answer · 2012-01-02 18:11:02Z

2

That's because your splitting is not being preserved:

tempCrfFC[i].split("\\s")[39] = "A";    //<-------
System.out.println("val: "+tempCrfFC[i].split("\\s")[39]);

If you look at that .split("\\s") returns an array and [39] = "A" part sets the 39th element to "A". But, the generated array is gone. And then you do the splitting again and print the 39th element of the new array generated by second split.

Try something as follows:

String[] parts = tempCrfFC[i].split("\\s");    //<-------
parts[39] = "A";
System.out.println("val: " + parts[39]);

answered Jan 2, 2012 at 18:11

Bhesh Gurung

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Comments

alf · Accepted Answer · 2012-01-02 18:21:14Z

1

Try

String[] tempCrfFC = crfFC;                //crfFC is a String[] itself
for(int i = 0; i < crfFC.length; i++) {
    String[] crfTok = tempCrfFC[i].split("\\s");
    if(crfTok.length == 40) {
        String[] parts = crfTok[39].split("/");
        if (parts[0].equals("O")) {
            Double v = Double.parseDouble(parts[1]);
            if (v <= d && (i == 0 || prevTagged != i-1)) {
                cfTok[39] = "A";    //<-------
                System.out.println("val: " + cfTok[39]);
                tempCrfFC[i] = join(cfTok);
                System.out.println("tempCrfFC: " + tempCrfFC[i]);
                prevTagged = i;
            }
         }
    }
}

where join is a method that joins your string back from an array.

edited Jan 2, 2012 at 18:21

answered Jan 2, 2012 at 18:14

alf

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Comments

Joop Eggen · Accepted Answer · 2012-01-02 18:15:33Z

String[] tempCrfFC = crfFC;                //crfFC is a String[] itself
for(int i = 0; i < crfFC.length; i++) {
    String[] crfTok = tempCrfFC[i].split("\\s");
    if(crfTok.length == 40) {
        if(crfTok[39].split("/")[0].equals("O")) {
            Double v = Double.parseDouble(crfTok[39].split("/")[1]);
            if (v <= d && (i == 0 || prevTagged != i-1)) {
                crfTok[39] = "A";    //<-------
                System.out.println("val: "+crfTok[39]);
                System.out.println("tempCrfFC: "+crfTok);
                prevTagged = i;
                StringBuilder joined = new StringBuilder();

                // Save in original array:
                for (String s : crfTok) {
                    if (joined.length() != 0)
                        joined.append(' ');
                    joined.append(s);
                }
                tempCrfFC[i] = joined.toString();
            }
         }
    }
}

alf · Accepted Answer · 2012-01-02 18:33:46Z

1

tempCrfFC[i].split("\s") will give you a new string array. So your code should be like below

 String[] test = tempCrfFC[i].split("\\s");
 test[39]="A"; //Assuming test array has at least 40 elements
 System.out.println(test[39]);

edited Jan 2, 2012 at 18:33

alf

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answered Jan 2, 2012 at 18:09

Pavan

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Comments

vivek_jonam · Accepted Answer · 2012-01-02 18:10:23Z

0

you are assigning the new value to a temporary array returned by the split() method and that new value is not replaced in the original string array,,

answered Jan 2, 2012 at 18:10

vivek_jonam

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Comments

david · Accepted Answer · 2012-01-02 18:24:58Z

0

You are assigning the "A" to one of the String objects which are resulting from the split(..) operation. But you have to note that any operations on the split-result are not updated on the orginal object. So you have to update the orignal string too.

Replace the line

tempCrfFC[i].split("\\s")[39] = "A"; //<-------

by something like

String[] splitted = tempCrfFC[i].split("\\s");
splitted[39] = "A";
tempCrfFC[i] = "";
for (String s : splitted) {
  tempCrfFC[i] += s;
}

The part within the for-loop depends on your aim how to concat/join the string parts again.

answered Jan 2, 2012 at 18:24

david

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