Java calculator add numbers to textfield

Question

I am making a calculator to test my skills in java. How can make the numbers to show up in the jTextfield until i pressed one button to calculate the numbers; i want every numbers to show up in the textfield. for example if i pressed 1 and zero i want the textfield to have 10.

int num;
JTextField in = new JTextField(20); // input field where numbers will up;

public void actionPerformed(ActionEvent e) {
    if (e.getSource() == bouttons.get(0)) {
        num = 0;
        in.setText("" + num);
    }
    if (e.getSource() == bouttons.get(1)) {
        int num = 1;
        in.setText("" + num);
    }
}

The screenshot

can you share the complete code. it seems you are not appending the text — Juned Ahsan, May 10 '13 at 14:36
See [this example](http://stackoverflow.com/a/7441804/418556) for tips. — Andrew Thompson, May 10 '13 at 15:10

An SO User · Answer 1 · 2013-05-12T05:50:52.190

To save yourself the hassle of a lot of if-else you can create an array of JButtons and go over them in a loop.
So button 0 will be at index 0.

Then, you can append the text to the JTextField as:

String alreadyDisplayed = in.getText(); //get the existing text
String toDisplay = alreadyDisplayed + Integer.toString(loopCounter);// append the position to the text
in.setText(toDisplay);// display the text

You can loop as follows:

for(int i=0;i<jbuttonArray.length;i++){
    if(e.getSource()==jbuttonArray[i]){
        //insert above code here;
    }
}

Here is the tutorial by Oracle on this subject: http://docs.oracle.com/javase/tutorial/uiswing/components/textfield.html

score 2 · Answer 2 · answered May 10 '13 at 14:36

2

You want to append the text to whatever already is there - try something like

in.setText(in.getText() + num) instead of in.setText("" + num)

answered May 10 '13 at 14:36

Mateusz

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score 1 · Answer 3 · answered May 10 '13 at 14:36

you should append with in.getText() instead of empty String

int num ;
JTextField in = new JTextField(20); // input field where numbers will up;
public void actionPerformed(ActionEvent e) {



    if (e.getSource() == bouttons.get(0)) {

        num =0;

        in.setText(in.getText() + num);

    }

    if (e.getSource() == bouttons.get(1)) {

        int num = 1;
        in.setText(in.getText() + num);

    }

}

Deepanshu · Answer 4 · 2019-12-02T08:50:49.627

You could add ActionListener to the numeric button. For eg: if you have a JButton b1 that add 1 to the textfield... You could use it like this:

    public void actionPerformed(ActionEvent e) {
        /* I'm using equals method because I feel that it is more reliable than '==' operator
         * but you can also use '=='
         */
        if(e.getSource().equals(b1){
            in.setText(in.getText + "1");
        }
    }

And similarly you could add other buttons for 1,2,3... and implement it like this.

Hope this will help you.... :-) :-)

Java calculator add numbers to textfield

4 Answers4