Why Does the Equal Button Not Work on My RPN Calculator?

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Discussion Overview

The discussion revolves around a user experiencing issues with the equal button on their RPN (Reverse Polish Notation) calculator implemented in Java. Participants explore the functionality of RPN calculators, the expected operations, and potential issues in the provided code.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about the functionality of the equal button in their RPN calculator code.
  • Another participant notes that RPN calculators do not typically use an equals sign, suggesting that the user may be misunderstanding how RPN operates.
  • A different participant clarifies the expected sequence of operations in RPN, emphasizing the use of an Enter button instead of an equals button.
  • The original poster confirms they have an Enter button but states that pressing it does not yield any result.
  • Another participant reiterates the correct sequence of key presses needed to perform an addition operation in RPN.
  • The original poster insists they understand how RPN works but continues to face issues with their implementation.

Areas of Agreement / Disagreement

Participants generally agree on the operational principles of RPN calculators, particularly the use of the Enter button. However, the original poster's specific issue with their code remains unresolved, with no consensus on the cause of the problem.

Contextual Notes

The discussion highlights potential misunderstandings about RPN operation and the specific implementation in the user's code, but does not resolve the underlying issue with the calculator's functionality.

ali11
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I have no idea what wrong my cods when I press = button of my calculator nothing happens.
can someone help me to fix my codes thanks.

Code: 
import java.util.Stack;
 import java.awt.*;
 import java.awt.event.*;
 import javax.swing.*;
 import java.math.*;
 import java.util.Vector;
 

public class Ahsan extends JFrame{
 Stack s = new Stack();
 
private JFrame f;
 private JPanel p1,p2;
 private JTextField jtfMain;
 private JButton jbtnOn, jbtnMRC, jbtnMminus, jbtnMadd, jbtnDivide, jbtnOff, jbtnSeven, jbtnEight, jbtnNine, jbtnMultiply,
 jbtnSqrt, jbtnFour, jbtnFive, jbtnSix, jbtnMinus, jbtnSq, jbtnOne, jbtnTwo, jbtnThree, jbtnPlus, jbtn1x, jbtnZero, jbtnDecimal,
 jbtnEqual, jbtnEnter;
 
char ch;
 Stack<String> cStack=new Stack<String>();
 public Ahsan() {
 


setSize(400,190);
 setTitle("Reverse Polish Notation Calculator");
 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 setLayout(new BorderLayout());
 
jtfMain = new JTextField("");
 
jbtnOn = new JButton("ON/AC");
 jbtnMRC = new JButton("MRC");
 jbtnMminus = new JButton("M-");
 jbtnMadd = new JButton("M+");
 jbtnDivide = new JButton("/");
 jbtnOff = new JButton("OFF");
 jbtnSeven = new JButton("7");
 jbtnEight = new JButton("8");
 jbtnNine = new JButton("9");
 jbtnMultiply = new JButton("X");
 jbtnSqrt = new JButton("SQRT");
 jbtnFour = new JButton("4");
 jbtnFive = new JButton("5");
 jbtnSix = new JButton("6");
 jbtnMinus = new JButton("-");
 jbtnSq = new JButton("SQ");
 jbtnOne = new JButton("1");
 jbtnTwo = new JButton("2");
 jbtnThree = new JButton("3");
 jbtnPlus = new JButton("+");
 jbtn1x = new JButton("1/x");
 jbtnZero = new JButton("0");
 jbtnDecimal = new JButton(".");
 jbtnEqual = new JButton("=");
 jbtnEnter = new JButton("ENTER");
 
p1 = new JPanel();
 p1.setLayout(new GridLayout(1,1));
 
p2 = new JPanel();
 p2.setLayout(new GridLayout(5,5));
 
p1.add(jtfMain);
 
p2.add(jbtnOn);
 p2.add(jbtnMRC);
 p2.add(jbtnMadd);
 p2.add(jbtnMminus);
 p2.add(jbtnDivide);
 p2.add(jbtnSeven);
 p2.add(jbtnEight);
 p2.add(jbtnNine);
 p2.add(jbtnMultiply);
 p2.add(jbtnSqrt);
 p2.add(jbtnFour);
 p2.add(jbtnFive);
 p2.add(jbtnSix);
 p2.add(jbtnMinus);
 p2.add(jbtnSq);
 p2.add(jbtnOne);
 p2.add(jbtnTwo);
 p2.add(jbtnThree);
 p2.add(jbtnPlus);
 p2.add(jbtn1x);
 p2.add(jbtnZero);
 p2.add(jbtnDecimal);
 p2.add(jbtnEqual);
 p2.add(jbtnEnter);
 p2.add(jbtnOff);
 
ButtonHandler buttonHandler=new ButtonHandler();
 jbtnOn.addActionListener(new ButtonHandler());
 jbtnMRC.addActionListener(new ButtonHandler());
 jbtnMminus.addActionListener(new ButtonHandler());
 jbtnDivide.addActionListener(new ButtonHandler());
 jbtnOff.addActionListener(new ButtonHandler());
 jbtnSeven.addActionListener(new ButtonHandler());
 jbtnEight.addActionListener(new ButtonHandler());
 jbtnNine.addActionListener(new ButtonHandler());
 jbtnMultiply.addActionListener(new ButtonHandler());
 jbtnSqrt.addActionListener(new ButtonHandler());
 jbtnFour.addActionListener(new ButtonHandler());
 jbtnFive.addActionListener(new ButtonHandler());
 jbtnSix.addActionListener(new ButtonHandler());
 jbtnMinus.addActionListener(new ButtonHandler());
 jbtnSq.addActionListener(new ButtonHandler());
 jbtnOne.addActionListener(new ButtonHandler());
 jbtnTwo.addActionListener(new ButtonHandler());
 jbtnThree.addActionListener(new ButtonHandler());
 jbtnPlus.addActionListener(new ButtonHandler());
 jbtn1x.addActionListener(new ButtonHandler());
 jbtnZero.addActionListener(new ButtonHandler());
 jbtnDecimal.addActionListener(new ButtonHandler());
 jbtnEqual.addActionListener(new ButtonHandler());
 jbtnEnter.addActionListener(new ButtonHandler());
 
add(p1, BorderLayout.NORTH);
 add(p2, BorderLayout.CENTER);
 
setVisible(true);
 }
 
public class enterHandler implements ActionListener
 {
 public void actionPerformed(ActionEvent evt)
 {
 int a;
 int b;
 
if (evt.getSource() == jbtnEnter)
 {
 //JButton hooked = (JButton) evt.getSource();
 
jtfMain.setText(jtfMain.getText() + " ");
 
String value = jtfMain.getText();
 
//if(value.lastIndexOf().equals("+"))
 //{
 String [] itemValue = value.split(" ");
 //System.out.println(itemValue.length);
 
for (int i=0;i<itemValue.length;i++)
 {
 cStack.push(itemValue[i]);
 }
 

if(cStack.pop().equals("+"))
 {
 
BigInteger first = new BigInteger(cStack.pop());
 BigInteger second = new BigInteger(cStack.pop());
 
first = first.add(second);
 cStack.push(first + "");
 }
 if(cStack.pop().equals("-"))
 {
 
BigInteger first = new BigInteger(cStack.pop());
 BigInteger second = new BigInteger(cStack.pop());
 
first = first.subtract(second);
 cStack.push(first + "");
 }
 
/*else if(cStack.pop().equals("-"))
 {
 BigInteger first = new BigInteger(cStack.pop());
 BigInteger second = new BigInteger(cStack.pop());
 
first = first.subtract(second);
 cStack.push(first + "");
 }*/
 //jtfMain.setText(cStack.pop());
 /*switch(ch)
 {
 case "/" : a = first.divide(second);
 }*/
 }
 }
 
}
 //}
 
public class ButtonHandler implements ActionListener
 {
 public void actionPerformed(ActionEvent evt)
 {
 JButton clicked = (JButton) evt.getSource();
 
if(clicked == jbtnOn)
 {
 jtfMain.setText("");
 }
 else if(clicked == jbtnOne)
 {
 jtfMain.setText(jtfMain.getText() + "1");
 //cStack.push(1);
 }
 else if(clicked== jbtnTwo)
 {
 jtfMain.setText(jtfMain.getText() + "2");
 //cStack.push(2);
 }
 else if(clicked== jbtnThree)
 {
 jtfMain.setText(jtfMain.getText() + "3");
 //cStack.push(3);
 }
 else if(clicked== jbtnFour)
 {
 jtfMain.setText(jtfMain.getText() + "4");
 //cStack.push(4);
 }
 else if(clicked== jbtnFive)
 {
 jtfMain.setText(jtfMain.getText() + "5");
 //cStack.push(5);
 }
 else if(clicked== jbtnSix)
 {
 jtfMain.setText(jtfMain.getText() + "6");
 //cStack.push(6);
 }
 else if(clicked== jbtnSeven)
 {
 jtfMain.setText(jtfMain.getText() + "7");
 //cStack.push(7);
 }
 else if(clicked== jbtnEight)
 {
 jtfMain.setText(jtfMain.getText() + "8");
 //cStack.push(8);
 }
 else if(clicked == jbtnNine)
 {
 jtfMain.setText(jtfMain.getText() + "9");
 //cStack.push(9);
 }
 else if(clicked == jbtnZero)
 {
 jtfMain.setText(jtfMain.getText() + "0");
 //add.numbers[];
 }
 else if(clicked == jbtnDivide)
 {
 jtfMain.setText(jtfMain.getText() + "/");
 //ch = '/';
 }
 
else if(clicked== jbtnMultiply)
 {
 jtfMain.setText(jtfMain.getText() + "X");
 
}
 else if(clicked== jbtnPlus)
 {
 jtfMain.setText(jtfMain.getText() + "+");
 //ch = 'a';
 }
 else if(clicked== jbtnMinus)
 {
 jtfMain.setText(jtfMain.getText() + "-");
 
}
 /*else if(clicked == jbtnEnter)
 {
 //cStack.push(numbers[0]);
 jtfMain.setText(jtfMain.getText() + " ");
 }*/
 else if(clicked == jbtnEqual)
 {
 jtfMain.setText(jtfMain.getText() + cStack.pop());
 }
 }
 }
 
public static void main(String[] args) {
 Ahsan main = new Ahsan();
 }
 }
 
Last edited by a moderator:
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Do not double post your questions.
 
I wouldn't know the first thing about java. But I do know that RPN calculators do not have an equals sign. They do not use an equals sign; it has no part to play in their operation. So if everything else works for your calculator, except the equals sign, then perhaps you are worrying unnecessarily?
 
Taking what NascentOxygen said into account, if all you did was press =, what did you expect to happen?

Instead of an = button, you should have an Enter button. With an RPN calculator, to add 5 and 3, you would do this:
Click 5
Click Enter
Click 3
Click +

The result should be 8.
 
I do have enter button but when i press it nothing happens
 
It sounds like you are not familiar with the code you are using.

To add two numbers, type these 4 keypresses:
5
enter
2
+
 
I know how RPN calculator works but the problem is when I put numbers and press enter I don't get any result. thanks
 
ali11 said:
I do have enter button but when i press it nothing happens

ali11 said:
I know how RPN calculator works but the problem is when I put numbers and press enter I don't get any result. thanks
What is supposed to happen when you press enter? And by that, I mean, what part of the code should you be looking at? Since this is code that you wrote, you should have some idea of how the pieces fit together.
 
ali11 said:
I do have enter button but when i press it nothing happens
Because you have it commented out.
 
  • #10
To subtract two numbers it should be like this
7
enter
1
-