CODEWITHSUNDEEP
java
Jon
Jon

Reputation: 113

Does StringBuilder not append whitespaces?

I am working on a web application using Woodstock component. In short, if the dropdown value equals to "PRIMARY KEY", the function should store the name of the table (from the textfield) into the String pk/primaryKey.

The problem I am facing currently is that the results obtained from the function is:

"abc"

instead of

"a, b, c"

Why is this happening?

public void addPK(TextField tf, DropDown dd, StringBuilder pk, int val) {
    if (((String) dd.getValue()).equals("PRIMARY KEY")) {
        if (val == 0) {
            pk.append((String) tf.getValue());
            val++;
        } else {
            pk.append(", " + (String) tf.getValue());
        }
    }
}


public String createButton1_action() {
    StringBuilder primaryKey = new StringBuilder();
    int pkCheck = 0;

    addPK(column_TF1, pkDropDown1, primaryKey, pkCheck);
    addPK(column_TF2, pkDropDown2, primaryKey, pkCheck);
    addPK(column_TF3, pkDropDown3, primaryKey, pkCheck);
    .
    .
}

Thank you.

Upvotes: 0

Views: 2053

Answers (3)

Ashish Aggarwal
Ashish Aggarwal

Reputation: 3026

pkcheck value is always zero when you calling your method 'addPK'. S for that either increment pkcheck value after every call or you can cheak with the value of your stringbuider length you can change your method like

Option 1.

public void addPK(TextField tf, DropDown dd, StringBuilder pk) {
    if (((String) dd.getValue()).equals("PRIMARY KEY")) {
        if (pk.length()== 0) {
            pk.append((String) tf.getValue());
        } else {
            pk.append(", ").append((String) tf.getValue());
        }
    }
}


Option 2.

public int addPK(TextField tf, DropDown dd, StringBuilder pk, int val) {
    if (((String) dd.getValue()).equals("PRIMARY KEY")) {
        if (val == 0) {
            pk.append((String) tf.getValue());
            val++;
        } else {
            pk.append(", " + (String) tf.getValue());
        }
    }
    return val;
}


public String createButton1_action() {
    StringBuilder primaryKey = new StringBuilder();
    int pkCheck = 0;

    pkCheck = addPK(column_TF1, pkDropDown1, primaryKey, pkCheck);
    pkCheck = addPK(column_TF2, pkDropDown2, primaryKey, pkCheck);
    pkCheck = addPK(column_TF3, pkDropDown3, primaryKey, pkCheck);
    .
    .
}

*And if your are using StringBuilder or StringBuffer the best practice is to use append operation instead of '+' operator

pk.append(", " + (String) tf.getValue());

replace with
pk.append(", ").append((String) tf.getValue());*

Upvotes: 3

epoch
epoch

Reputation: 16615

have you debugged? val stays at 0 the whole time. modifying it within your method has no effect.

i.e. executing val++ will not change pkCheck

for reference: java-is-pass-by-value

Upvotes: 2

stinepike
stinepike

Reputation: 54692

Because you are sending a val parameter with the value 0

  int pkCheck = 0;   

    addPK(column_TF1, pkDropDown1, primaryKey, pkCheck); // value is 0 here

and in addpK method

if (val == 0) {
    pk.append((String) tf.getValue());
    val++;
}

So to get the desired result you need to set the value of pCheck to other values rather than 0

Upvotes: 2

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