Scientific Calculator in Java

import javax.swing.*;
import javax.swing.border.BevelBorder;
import java.awt.*;
import java.awt.event.*;
import java.util.*;

class Calculator {

	JFrame frmCalculator;
	String result="",expression="";
	ArrayList<String> token=new ArrayList<String>();
	
	boolean num=false;  
	boolean dot=false;  
	
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				try {
					Calculator window = new Calculator();
					window.frmCalculator.setVisible(true);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
	}

	Calculator() {
		initialize();
	}

	int precedence(String x)
	{
		int p=10;
		switch(x) {
		case "+":
			p=1;
			break;
		case "-":
			p=2;
			break;
		case "x":
			p=3;
			break;
		case "/":
			p=4;
			break;
		case "^":
			p=6;
			break;
		case "!":
			p=7;
			break;
		}
	
		return p;
	}
	
	//operator checking
	private boolean isoperator(String x)
	{
		if(x.equals("+") || x.equals("-") || x.equals("x") || x.equals("/") || x.equals("sqrt") || x.equals("^") || x.equals("!") || x.equals("sin") || x.equals("cos") || x.equals("tan") || x.equals("ln") || x.equals("log"))
			return true;
		else 
			return false;
	}
	
	private String infixTopostfix()
	{
		Stack<String> s=new Stack<String>();
		String y;
		int flag;
		String p="";   
		token.add(")");
		s.push("(");
		for(String i: token) {
			if(i.equals("(")){
				s.push(i);
			}else if(i.equals(")")){
				y=s.pop();
				while(!y.equals("("))
				{
					p=p+y+",";
					y=s.pop();
				}
			}else if(isoperator(i)){
				y=s.pop();
				flag=0;
				if(isoperator(y) && precedence(y)>precedence(i)){
					p=p+y+",";
					flag=1;
				}
				if(flag==0)
					s.push(y);
				
				s.push(i);
			}else{
				p=p+i+",";
			}
		}
		while(!s.empty()) {
			y=s.pop();
			if(!y.equals("(") && !y.equals(")")) {
				p+=y+",";
			}
		}
		return p;
	}

	//factorial method
	private double factorial(double y) {
		double fact=1;
		if(y==0 || y==1) {
			fact=1;
		}else {
			for(int i=2; i<=y; i++) {
				fact*=i;
			}
		}
		return fact;
	}
	
	//for actual calculation with binary operators
	private double calculate(double x,double y,String c)
	{
		double res=0;
		switch(c)
		{
			case "-":
				res= x-y;
				break;
			case "+":
				res= x+y;
				break;
			case "x":
				res= x*y;
				break;
			case "/":
				res= x/y;
				break;
			case "^":
				res= Math.pow(x,y);
				break;
			default :
				res= 0;
		}
		return res;
	}
	
	//calculation with unary operators
	private double calculate(double y,String c) {
		double res=0;
		switch(c) {
		case "log":
			res = Math.log10(y);
			break;
		case "sin":
			res= Math.sin(y);
			break;
		case "cos":
			res = Math.cos(y);
			break;
		case "tan":
			res =Math.tan(y);
			break;
		case "ln":
			res= Math.log(y);
			break;
		case "sqrt":
			res= Math.sqrt(y);
			break;
		case "!":
			res=factorial(y);
			break;
		}
		return res;
	}

	private double Eval(String p)
	{	
		String tokens[] = p.split(",");
		ArrayList<String> token2=new ArrayList<String>();
		for(int i=0; i<tokens.length; i++) {
			if(! tokens[i].equals("") && ! tokens[i].equals(" ") && ! tokens[i].equals("\n") && ! tokens[i].equals("  ")) {
				token2.add(tokens[i]);  // tokens from post fix form p actual tokens for calculation
			}
		}
		
		Stack<Double> s=new Stack<Double>();
		double x,y;
		for(String  i:token2) {
			if(isoperator(i)){
				//if it is unary operator or function
				if(i.equals("sin") ||i.equals("cos") ||i.equals("tan") ||i.equals("log") || i.equals("ln") || i.equals("sqrt") || i.equals("!")) {
					y=s.pop();
					s.push(calculate(y,i));
				}else {
					//for binary operators
					y=s.pop();
					x=s.pop();
					s.push(calculate(x,y,i));
				}
			}else{
				if(i.equals("pi"))
					s.push(Math.PI);
				else if(i.equals("e"))
					s.push(Math.E);
				else
					s.push(Double.valueOf(i));
			}
		}
		double res=1;
		while(!s.empty()) {
			res*=s.pop();
		}
		return res;  //final result
	}

	//actual combined method for calculation 
	private void calculateMain() {
		String tokens[]=expression.split(",");
		for(int i=0; i<tokens.length; i++) {
			if(! tokens[i].equals("") && ! tokens[i].equals(" ") && ! tokens[i].equals("\n") && ! tokens[i].equals("  ")) {
				token.add(tokens[i]);  //adding token to token array list from expression 
			}
		}
		try {
			double res = Eval(infixTopostfix());
			result= Double.toString(res);
		}catch(Exception e) {}
	}
	
	
	//design of the frame with their action listner
	private void initialize() {
		frmCalculator = new JFrame();
		frmCalculator.setResizable(false);
		frmCalculator.setTitle("Calculator");
		frmCalculator.getContentPane().setBackground(new Color(172, 170, 255));
		frmCalculator.getContentPane().setFont(new Font("Calibri", Font.PLAIN, 15));
		frmCalculator.getContentPane().setForeground(SystemColor.windowBorder);
		frmCalculator.getContentPane().setLayout(null);
		
		JPanel textPanel = new JPanel();
		textPanel.setBorder(new BevelBorder(BevelBorder.LOWERED, null, null, null, null));
		textPanel.setBounds(34, 25, 316, 80);
		frmCalculator.getContentPane().add(textPanel);
		textPanel.setLayout(null);
		
		JLabel exprlabel = new JLabel("");
		exprlabel.setBackground(SystemColor.control);
		exprlabel.setFont(new Font("Yu Gothic UI Light", Font.PLAIN, 20));
		exprlabel.setHorizontalAlignment(SwingConstants.RIGHT);
		exprlabel.setForeground(UIManager.getColor("Button.disabledForeground"));
		exprlabel.setBounds(2, 2, 312, 27);
		textPanel.add(exprlabel);
		
		JTextField textField = new JTextField();
		exprlabel.setLabelFor(textField);
		textField.setHorizontalAlignment(SwingConstants.RIGHT);
		textField.setBackground(SystemColor.control);
		textField.setEditable(false);
		textField.setText("0");
		textField.setBorder(null);
		textField.setFont(new Font("Yu Gothic UI Light", textField.getFont().getStyle(), 32));
		textField.setBounds(2, 30, 312, 49);
		textPanel.add(textField);
		textField.setColumns(10);
		
		JPanel butttonPanel = new JPanel();
		butttonPanel.setBorder(new BevelBorder(BevelBorder.LOWERED, null, null, null, null));
		butttonPanel.setBackground(SystemColor.inactiveCaptionBorder);
		butttonPanel.setBounds(34, 120, 316, 322);
		frmCalculator.getContentPane().add(butttonPanel);
		butttonPanel.setLayout(new GridLayout(0, 5, 0, 0));
		
		//clear button 
		JButton button1 = new JButton("C");
		button1.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				textField.setText("0");
				exprlabel.setText("");
				expression ="";
				token.clear();
				result="";
				num=false;
				dot=false;
			}
		});
		button1.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button1);
		
		//delete button
		JButton button2 = new JButton("DEL");
		button2.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				String s=textField.getText();
				if(s != "0" && s.length() > 1) {
					String newString = s.substring(0,s.length()-1);
					textField.setText(newString);
					if(expression.charAt(expression.length()-1)=='.') {
						dot=false;
					}
					if(expression.charAt(expression.length()-1) == ',') {
						expression = expression.substring(0,expression.length()-2);
					}else {
						expression = expression.substring(0,expression.length()-1);
					}
				}else {
					textField.setText("0");
					expression="";
				}
			}
		});
		button2.setFont(new Font("Calibri Light", Font.PLAIN, 14));
		butttonPanel.add(button2);
		
		
		//button for constant pi
		JButton button3 = new JButton("<html><body><span>π</span></body></html>");
		button3.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		button3.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+Character.toString((char)960));
				}else {
					textField.setText(Character.toString((char)960));
				}
				expression += ",pi";
				num=false;
				dot=false;
			}
		});
		butttonPanel.add(button3);
		
		//button for x^Y
		JButton button4 = new JButton("<html><body><span>X<sup>y</sup></span></body></html>");
		button4.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"^");
					expression+=",^";
				}else {
					textField.setText("0^");
					expression += ",0,^";
				}
				num=false;
				dot=false;
			}
		});
		button4.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button4);
		
		//factorial button
		JButton buttton5 = new JButton("x!");
		buttton5.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"!");
					expression+=",!";
				}else {
					textField.setText("0!");
					expression+=",0,!";
				}
				num=false;
				dot=false;
			}
		});
		buttton5.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(buttton5);
		
		//button for sin
		JButton button6 = new JButton("sin");
		button6.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"sin(");
				}else {
					textField.setText("sin(");
				}
				expression+=",sin,(";
				num=false;
				dot=false;
			}
		});
		button6.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button6);
		
		JButton button7 = new JButton("(");
		button7.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"(");
				}else {
					textField.setText("(");
				}
				expression+=",(";
				num=false;
				dot=false;
			}
		});
		button7.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button7);
		
		JButton button8 = new JButton(")");
		button8.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+")");
				}else {
					textField.setText(")");
				}
				expression+=",)";
				num=false;
				dot=false;
			}
		});
		button8.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button8);
		
		JButton button9 = new JButton("e");
		button9.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"e");
				}else {
					textField.setText("e");
				}
				expression+=",e";
				num=false;
				dot=false;
			}
		});
		button9.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button9);
		
		//button for squre root
		JButton button10 = new JButton("<html><body><span>√</span></body></html>");
		button10.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+Character.toString((char)8730));
				}else {
					textField.setText(Character.toString((char)8730));
				}
				expression+=",sqrt";
				num=false;
				dot=false;
			}
		});
		button10.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button10);
		
		JButton button11 = new JButton("cos");
		button11.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"cos(");
				}else {
					textField.setText("cos(");
				}
				expression+=",cos,(";
				num=false;
				dot=false;
			}
		});
		button11.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button11);
		
		JButton button12 = new JButton("7");
		button12.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"7");
				}else {
					textField.setText("7");
				}
				if(num) {
					expression+="7";
				}else {
					expression+=",7";
				}
				num=true;
			}
		});
		button12.setBackground(new Color(220, 220, 220));
		button12.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button12);
		
		JButton button13 = new JButton("8");
		button13.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"8");
				}else {
					textField.setText("8");
				}
				if(num) {
					expression+="8";
				}else {
					expression+=",8";
				}
				num=true;
			}
		});
		button13.setBackground(new Color(220, 220, 220));
		button13.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button13);
		
		JButton button14 = new JButton("9");
		button14.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"9");
				}else {
					textField.setText("9");
				}
				if(num) {
					expression+="9";
				}else {
					expression+=",9";
				}
				num=true;
			}
		});
		button14.setBackground(new Color(220, 220, 220));
		button14.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button14);
		
		
		//button for division operator
		JButton button15 = new JButton("<html><body><span>÷</span></body></html>");
		button15.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				String s=textField.getText();
				if(s.equals("0")) {
					expression+="0";
				}
				if(s.charAt(s.length()-1)== '-' || s.charAt(s.length()-1)== 'x' || s.charAt(s.length()-1) == '+') {
					String newString = s.substring(0,s.length()-1);
					textField.setText(newString+Character.toString((char)247));
					expression = expression.substring(0,expression.length()-1);
					expression += "/";
				}else if(s.charAt(s.length()-1)!= (char)247) {	
					textField.setText(s+Character.toString((char)247));	
					expression+=",/";
				}else {
					textField.setText(s);	
				}
				num=false;
				dot=false;
			}
		});
		button15.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button15);
		
		JButton button16 = new JButton("tan");
		button16.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"tan(");
				}else {
					textField.setText("tan(");
				}
				expression+=",tan,(";
				num=false;
				dot=false;
			}
		});
		button16.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button16);
		
		JButton button17 = new JButton("4");
		button17.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"4");
				}else {
					textField.setText("4");
				}
				if(num) {
					expression+="4";
				}else {
					expression+=",4";
				}
				num=true;
			}
		});
		button17.setBackground(new Color(220, 220, 220));
		button17.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button17);
		
		JButton button18 = new JButton("5");
		button18.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"5");
				}else {
					textField.setText("5");
				}
				if(num) {
					expression+="5";
				}else {
					expression+=",5";
				}
				num=true;
			}
		});
		button18.setBackground(new Color(220, 220, 220));
		button18.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button18);
		
		JButton button19 = new JButton("6");
		button19.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"6");
				}else {
					textField.setText("6");
				}
				if(num) {
					expression+="6";
				}else {
					expression+=",6";
				}
				num=true;
			}
		});
		button19.setBackground(new Color(220, 220, 220));
		button19.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button19);
		
		JButton button20 = new JButton("x");
		button20.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				
				String s=textField.getText();
				if(s.equals("0")) {
					expression+="0";
				}
				if(s.charAt(s.length()-1)== '-' || s.charAt(s.length()-1)== '+' || s.charAt(s.length()-1) == (char)(247)) {
					String newString = s.substring(0,s.length()-1);
					newString += "x";
					textField.setText(newString);
					expression = expression.substring(0,expression.length()-1);
					expression += "x";
				}else if(s.charAt(s.length()-1)!= 'x') {
					s += "x";	
					textField.setText(s);
					expression+=",x";
				}else {
					textField.setText(s);	
				}
				num=false;
				dot=false;
			}
		});
		button20.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button20);
		
		JButton button21 = new JButton("ln");
		button21.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"ln(");
				}else {
					textField.setText("ln(");
				}
				expression+=",ln,(";
				num=false;
				dot=false;
			}
		});
		button21.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button21);
		
		JButton button22 = new JButton("1");
		button22.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"1");
				}else {
					textField.setText("1");
				}
				if(num) {
					expression+="1";
				}else {
					expression+=",1";
				}
				num=true;
			}
		});
		button22.setBackground(new Color(220, 220, 220));
		button22.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button22);
		
		JButton button23 = new JButton("2");
		button23.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"2");
				}else {
					textField.setText("2");
				}
				if(num) {
					expression+="2";
				}else {
					expression+=",2";
				}
				num=true;
			}
		});
		button23.setBackground(new Color(220, 220, 220));
		button23.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button23);
		
		JButton button24 = new JButton("3");
		button24.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"3");
				}else {
					textField.setText("3");
				}
				if(num) {
					expression+="3";
				}else {
					expression+=",3";
				}
				num=true;
			}
		});
		button24.setBackground(new Color(220, 220, 220));
		button24.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button24);
		
		JButton button25 = new JButton("-");
		button25.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				String s=textField.getText();
				if(s.equals("0")) {
					expression+="0";
				}
				if(s.charAt(s.length()-1)== '+') {
					String newString = s.substring(0,s.length()-1);
					newString += "-";
					expression = expression.substring(0,expression.length()-1);
					expression += "-";
					textField.setText(newString);
				}else if(s.charAt(s.length()-1)!= '-') {
					s += "-";	
					textField.setText(s);
					expression += ",-";
				}else {
					textField.setText(s);	
				}
				num=false;
				dot=false;
			}
		});
		button25.setFont(new Font("Calibri Light", Font.BOLD, 23));
		butttonPanel.add(button25);
		
		JButton button26 = new JButton("<html><body><span>log<sub>10</sub></span></body></html>");
		button26.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		button26.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if(! "0".equals(textField.getText())) {
					textField.setText(textField.getText()+"log(");
				}else {
					textField.setText("log(");
				}
				expression+=",log,(";
				num=false;
				dot=false;
			}
		});
		butttonPanel.add(button26);
		
		JButton button27 = new JButton(".");
		button27.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				String s=textField.getText();
				if(s.charAt(s.length()-1)!= '.') {
					if(num && dot==false) {
						expression+=".";
						s += ".";
					}else if(num==false && dot ==false){
						expression+=",.";
						s += ".";
					}
				}
				num=true;
				dot=true;
				textField.setText(s);	
			}
		});
		button27.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button27);
		
		JButton button28 = new JButton("0");
		button28.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				if("0".equals(textField.getText())) {
					textField.setText("0");
				}else {
					textField.setText(textField.getText()+"0");
					if(num) {
						expression+="0";
					}
					else {
						expression+=",0";
					}
				}
				num=true;
			}
		});
		button28.setBackground(new Color(220, 220, 220));
		button28.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button28);
		
		
		//actual functioning on clicking = button
		JButton button29 = new JButton("=");
		button29.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {	
				calculateMain();
					String s="";
					token.remove(token.size()-1);
					for(String i: token) {
						if(i.equals("/")) {
							s+=Character.toString((char)247);
						}else if(i.equals("sqrt")) {
							s+=Character.toString((char)8730);
						}else if(i.equals("pi")) {
							s+=Character.toString((char)960);
						}else {
							s+=i;
						}
					}
					exprlabel.setText(s+"=");
					textField.setText(result);
					
					expression = result;
					dot=true;
					num=true;
				token.clear();
			}
		});
		button29.setBackground(Color.ORANGE);
		button29.setFont(new Font("Calibri Light", Font.PLAIN, 22));
		butttonPanel.add(button29);
		
		JButton button30 = new JButton("+");
		button30.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				String s=textField.getText();
				if(s.equals("0")) {
					expression+="0";
				}
				if(s.charAt(s.length()-1)== '-' || s.charAt(s.length()-1)== 'x' || s.charAt(s.length()-1) == (char)(247)) {
					String newString = s.substring(0,s.length()-1);
					newString += "+";
					textField.setText(newString);
					expression = expression.substring(0,expression.length()-1);
					expression += "+";
				}else if(s.charAt(s.length()-1)!= '+') {
					s += "+";	
					textField.setText(s);
					expression+=",+";
				}else {
					textField.setText(s);	
				}
				num=false;
				dot=false;
			}
		});
		button30.setFont(new Font("Calibri Light", Font.PLAIN, 17));
		butttonPanel.add(button30);
		frmCalculator.setBounds(200, 100, 400, 500);
		frmCalculator.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}
}