Java Example: GUI

Basically, there are three steps to make GUI program:

1. Define Frame or Applet to hold components
2.  Add GUI components to Frame. Use layout manager to determine position
3.  Add actions to GUI. By adding event listeners to GUI components

 


The codes below show an event listener (handle button clicking) to calculate simple math calculation: addition, subtraction, multiplication, and division

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton1ActionPerformed
// TODO add your handling code here:
    
     try{  
        FileWriter fw = new FileWriter("db.txt", true);
        BufferedWriter bw = new BufferedWriter(fw);
        PrintWriter pw = new PrintWriter(bw);
       
        double total = 0.0, n1=0.0, n2=0.0;
        String insert, ops;
       
        insert = num1.getText();
        n1 = Integer.parseInt(insert);
       
        insert = num2.getText();
        n2 = Integer.parseInt(insert);
       
        ops = (String) arithmetic.getSelectedItem();
       
        if(ops.equalsIgnoreCase("+"))
            total = n1 + n2;
        else if(ops.equalsIgnoreCase("-"))
            total = n1 - n2;
        else if(ops.equalsIgnoreCase("/"))
            total = n1 / n2;
        else if(ops.equalsIgnoreCase("*"))
            total = n1 * n2;
       
        insert = String.valueOf(total);
       
        pw.append(n1 + "," + n2 + "," + ops + "," + total );
        pw.println();
       
        answer.setText(insert);
       
        pw.close();
       
     }
     catch(FileNotFoundException fnfe)
     {
        System.out.print(fnfe.getMessage());
     }
     catch(IOException ioe)
     {
        System.out.print(ioe.getMessage());
     }
    }//GEN-LAST:event_jButton1ActionPerformed

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