can somebody help. i m getting following errors. i m creating postfix calc
C:\Users\Hamza\Pictures\CalcGUIPanel.java:204: int cannot be dereferenced
Integer arg2=resultValue.pop();
^
C:\Users\Hamza\Pictures\CalcGUIPanel.java:205: int cannot be dereferenced
resultValue.push(resultValue.pop()+arg2);
^
C:\Users\Hamza\Pictures\CalcGUIPanel.java:205: operator + cannot be applied to <any>,java.lang.Integer
resultValue.push(resultValue.pop()+arg2);
^
C:\Users\Hamza\Pictures\CalcGUIPanel.java:205: int cannot be dereferenced
resultValue.push(resultValue.pop()+arg2);
^
C:\Users\Hamza\Pictures\CalcGUIPanel.java:211: int cannot be dereferenced
Integer arg2=resultValue.pop();
^
C:\Users\Hamza\Pictures\CalcGUIPanel.java:212: int cannot be dereferenced
resultValue.push(resultValue.pop()-arg2);
^
C:\Users\Hamza\Pictures\CalcGUIPanel.java:212: int cannot be dereferenced
resultValue.push(resultValue.pop()-arg2);
^
C:\Users\Hamza\Pictures\CalcGUIPanel.java:219: int cannot be dereferenced
Integer arg2=resultValue.pop();
^
C:\Users\Hamza\Pictures\CalcGUIPanel.java:220: int cannot be dereferenced
resultValue.push(resultValue.pop()*arg2);
^
C:\Users\Hamza\Pictures\CalcGUIPanel.java:220: int cannot be dereferenced
resultValue.push(resultValue.pop()*arg2);
^
C:\Users\Hamza\Pictures\CalcGUIPanel.java:227: int cannot be dereferenced
Integer arg2=resultValue.pop();
^
C:\Users\Hamza\Pictures\CalcGUIPanel.java:228: int cannot be dereferenced
resultValue.push(resultValue.pop()-arg2);
^
C:\Users\Hamza\Pictures\CalcGUIPanel.java:228: int cannot be dereferenced
resultValue.push(resultValue.pop()-arg2);
^
13 errors

Tool completed with exit code 1

import java.util.Stack;
import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import javax.swing.event.*;
import java.util.Scanner;


public class CalcGUIPanel extends JPanel
{


//--\- Component referenced during execution

 private JTextField displayField; // display result / input.

 //--\- Variables representing state of the calculator

 private boolean startNumber = true; // true: num key next

 private int resultValue = 0; // result so far

 private String previousOp = "="; // previous operation

 Stack<String> cStack=new Stack<String>();

 public CalcGUIPanel()
 {

 //--\- Display field

 displayField = new JTextField();

JButton clearButton = new JButton("CLEAR");



clearButton.addActionListener(new ClearListener());



 //--\- One listener for all numeric keys.

 ActionListener numListener = new NumListener();

 //--\- Layout numeric keys in a grid. Generate the buttons

 // in a loop from the chars in a string.

 String buttonOrder = "789456123 0 ";

 JPanel buttonPanel = new JPanel(new GridLayout(5, 3));

 for (int i = 0; i < buttonOrder.length(); i++) {



 String keyTop = buttonOrder.substring(i, i+1);

 if (keyTop.equals(" ")) {

 buttonPanel.add(new JLabel(""));

 } else {

 JButton b = new JButton(keyTop);

 b.addActionListener(numListener);




 buttonPanel.add(b);

 }

 }


 //--\- One ActionListener to use for all operator buttons.

 ActionListener opListener = new OpListener();

 //--\- Create panel with gridlayout to hold operator buttons.

 // Use array of button names to create buttons in a loop.

 JPanel opPanel = new JPanel(new GridLayout(5, 1));

 String[] opOrder = {"+", "-", "*", "/", "enter"};

 for (int i = 0; i < opOrder.length; i++) {

 JButton b = new JButton(opOrder[i]);
  {

 cStack.push(opOrder[i]);
 		 }



 b.addActionListener(opListener);

cStack.push("1");
cStack.push("2");
cStack.push("3");
cStack.push("4");
cStack.push("5");
cStack.push("6");
cStack.push("7");
cStack.push("8");
cStack.push("9");
cStack.push("0");
 cStack.push("+");
  cStack.push("-");
  cStack.push("*");
  cStack.push("/");
  cStack.push("enter");




 opPanel.add(b);

 }

 //--\- Layout the top-level panel.

 this.setLayout(new BorderLayout());

 this.add(displayField, BorderLayout.NORTH );

 this.add(buttonPanel , BorderLayout.CENTER);

 this.add(opPanel , BorderLayout.EAST );

this.add(clearButton , BorderLayout.SOUTH );

 }//end constructor

 //====================================================== action_clear

 /*\* Called by Clear btn action listener and elsewhere.*/

 private void action_clear() {

 startNumber = true;

 displayField.setText("0");

 resultValue = 0;
 int arg2;

 previousOp = "=";

 }

 // inner listener class OpListener

 /*\* Listener for all op buttons. \*/

 class OpListener implements ActionListener {

 public void actionPerformed(ActionEvent e) {

 // The calculator is always in one of two states.

 // 1. A number must be entered \-\- this operator is wrong.

 // 2. An operator must be entered \-\- we're ok.
 if (startNumber) { // Error: needed number, not operator

 action_clear();

 displayField.setText("ERROR");

 } else {



 startNumber = true; // Next thing must be a number


try {

 String displayText = displayField.getText();

 int currentValue = Integer.parseInt(displayText);


 if (previousOp.equals("=")) {
 cStack.push(resultValue + "");





 }

  else if (previousOp.equals("+")) {
	  Integer arg2=resultValue.pop();
	  	 resultValue.push(resultValue.pop()+arg2);




 }  else if (previousOp.equals("-")) {
	 Integer arg2=resultValue.pop();
	 resultValue.push(resultValue.pop()-arg2);





 } else if (previousOp.equals("*")) {
	Integer arg2=resultValue.pop();
	 resultValue.push(resultValue.pop()*arg2);



 } else if (previousOp.equals("/")) {
	cStack.pop().equals("/");

		Integer arg2=resultValue.pop();
	 resultValue.push(resultValue.pop()-arg2);
 ;

 }

 displayField.setText("" + resultValue);
 } catch (NumberFormatException ex) {

 action_clear();

 displayField.setText("Error");

}


 //--\- set \_previousOp for the next operator.

 previousOp = e.getActionCommand();

 }//endif \_startNumber

 }//endmethod

 }//end class

 //////////////////////////////////// inner listener class ClearListener

 // Action listener for numeric keys

 class NumListener implements ActionListener {

 public void actionPerformed(ActionEvent e) {

 String digit = e.getActionCommand(); // Get text from button

 if (startNumber) {

 // This is the first digit, clear field and set

 displayField.setText(digit);

 startNumber = false;

 } else {

 // Add this digit to the end of the display field

 displayField.setText(displayField.getText() + digit);

 }

 }

 }//end class

 //inner listener class ClearListener

class ClearListener implements ActionListener {

public void actionPerformed(ActionEvent e) {

action_clear();
}
}
}

resultValue is an int, so it doesn't have any methods - so you can't have
resultValue.pop()
which looks like an attempt to call a pop() method on an int that has no methods.

This article has been dead for over six months. Start a new discussion instead.