Calc.java

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
class Calc
{
	boolean opstate,ispoint=false;
	JPanel p;
	JButton invert,zero,point,solve,one,two,three,four,five,six,seven,eight,nine,plus,minus,multiply,divide,back,cancel,cancele;
	JTextField ip;
	JTextField exp;
	Calculate cobj=new Calculate();
	Calc()
	{
		JFrame f=new JFrame("Calculator");
		f.setLayout(null);
		f.addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});
		p=new JPanel();
		p.setLayout(null);
		p.setBounds(0,0,400,400); 
		invert=new JButton("\u00B1");
		invert.setBounds(50,280,80,30);
		zero=new JButton("0");
		zero.setBounds(130,280,80,30);
		point=new JButton(".");
		point.setBounds(210,280,80,30);
		solve=new JButton("=");
		solve.setBounds(290,280,80,30);
		one=new JButton("1");
		one.setBounds(50,250,80,30);
		two=new JButton("2");
		two.setBounds(130,250,80,30);
		three=new JButton("3");
		three.setBounds(210,250,80,30);
		four=new JButton("4");
		four.setBounds(50,220,80,30);
		five=new JButton("5");
		five.setBounds(130,220,80,30);
		six=new JButton("6");
		six.setBounds(210,220,80,30);
		seven=new JButton("7");
		seven.setBounds(50,190,80,30);
		eight=new JButton("8");
		eight.setBounds(130,190,80,30);
		nine=new JButton("9");
		nine.setBounds(210,190,80,30);
		plus=new JButton("\u002B");
		plus.setBounds(290,250,80,30);
		minus=new JButton("\u2212");
		minus.setBounds(290,220,80,30);
		multiply=new JButton("\u00D7");
		multiply.setBounds(290,190,80,30);
		divide=new JButton("\u00F7");
		divide.setBounds(290,160,80,30);
		back=new JButton("\u232B");
		back.setBounds(210,160,80,30);
		cancel=new JButton("C");
		cancel.setBounds(130,160,80,30);
		cancele=new JButton("CE");
		cancele.setBounds(50,160,80,30);
		ip=new JTextField("0");
		ip.setBounds(50,130,320,30);
		ip.setHorizontalAlignment(JTextField.RIGHT);
		ip.setEditable(false);
		exp=new JTextField("");
		exp.setBounds(50,95,320,30);
		exp.setHorizontalAlignment(JTextField.RIGHT);
		exp.setEditable(false);
		ActionListener al=new ActionListener(){
			public void actionPerformed(ActionEvent ae){
				String inp=ip.getText();
				if(inp.equals("0")||opstate)
				{
					inp="";
				}
				if(ae.getSource()==zero)
					ip.setText(inp+"0");
				else if(ae.getSource()==one)
					ip.setText(inp+"1");
				else if(ae.getSource()==two)
					ip.setText(inp+"2");
				else if(ae.getSource()==three)
					ip.setText(inp+"3");
				else if(ae.getSource()==four)
					ip.setText(inp+"4");
				else if(ae.getSource()==five)
					ip.setText(inp+"5");
				else if(ae.getSource()==six)
					ip.setText(inp+"6");
				else if(ae.getSource()==seven)
					ip.setText(inp+"7");
				else if(ae.getSource()==eight)
					ip.setText(inp+"8");
				else if(ae.getSource()==nine)
					ip.setText(inp+"9");
				else if(ae.getSource()==invert)
				{
					if(inp.equals(""))
						ip.setText("0");
					else if(inp.substring(0,1).equals("~"))
						ip.setText(inp.substring(1,inp.length()));
					else
						ip.setText("~"+inp);
				}
				else if(ae.getSource()==point)
				{
					if(ispoint&&!opstate)
						return;
					if(inp.equals("")||opstate)
						ip.setText("0.");
					else
						ip.setText(inp+".");
					ispoint=true;
				}
				opstate=false;
			}
		};
		ActionListener al1=new ActionListener(){
			public void actionPerformed(ActionEvent ae){
				String inp=ip.getText();
				if(inp.equals("Invalid"))
					return;
				if(opstate)
					opstate=false;
				if(opercheck())
					inp="";
				ispoint=false;
				if(ae.getSource()==plus)
				{
					exp.setText(exp.getText()+inp+"+");
					ip.setText("0");
				}
				else if(ae.getSource()==minus)
				{
					exp.setText(exp.getText()+inp+"-");
					ip.setText("0");
				}
				else if(ae.getSource()==multiply)
				{
					exp.setText(exp.getText()+inp+"*");
					ip.setText("0");
				}
				else if(ae.getSource()==divide)
				{
					exp.setText(exp.getText()+inp+"/");
					ip.setText("0");
				}
			}
		};
		ActionListener al2=new ActionListener(){
			public void actionPerformed(ActionEvent ae){
				String inp=ip.getText();
				if(inp.equals("Invalid"))
					return;
				if(ae.getSource()==back)
				{
					if(opstate)
						return;
					ispoint=false;
					if(!inp.equals("0"))
					{
						if(inp.substring(inp.length()-1,inp.length()).equals("."))
							ispoint=false;
						ip.setText(inp.substring(0,inp.length()-1));
					}
					if(ip.getText().equals(""))
						ip.setText("0");
				}
				else if(ae.getSource()==cancel)
				{
					ispoint=false;
					exp.setText("");
					ip.setText("0");
				}
				else if(ae.getSource()==cancele)
				{
					ispoint=false;
					ip.setText("0");
				}
			}
		};
		ActionListener al3=new ActionListener(){
			public void actionPerformed(ActionEvent ae){
				if(ip.getText().equals("Invalid"))
					return;
				String send=exp.getText()+ip.getText();
				cobj.setExpression(send);
				exp.setText("");
				ip.setText(cobj.getResult());
				opstate=true;
			}
		};
		zero.addActionListener(al);
		one.addActionListener(al);
		two.addActionListener(al);
		three.addActionListener(al);
		four.addActionListener(al);
		five.addActionListener(al);
		six.addActionListener(al);
		seven.addActionListener(al);
		eight.addActionListener(al);
		nine.addActionListener(al);
		invert.addActionListener(al);
		point.addActionListener(al);
		plus.addActionListener(al1);
		minus.addActionListener(al1);
		multiply.addActionListener(al1);
		divide.addActionListener(al1);
		back.addActionListener(al2);
		cancel.addActionListener(al2);
		cancele.addActionListener(al2);
		solve.addActionListener(al3);
		p.add(invert);
		p.add(point);
		p.add(zero);
		p.add(solve);
		p.add(one);
		p.add(two);
		p.add(three);
		p.add(four);
		p.add(five);
		p.add(six);
		p.add(seven);
		p.add(eight);
		p.add(nine);
		p.add(plus);
		p.add(minus);
		p.add(multiply);
		p.add(divide);
		p.add(back);
		p.add(cancel);
		p.add(cancele);
		p.add(ip);
		p.add(exp);
		f.add(p);
		f.setSize(400,400);
		f.setVisible(true);
	}
	boolean opercheck()
	{
		String chk=exp.getText();
		String inex=ip.getText();
		if(chk.equals(""))
			return false;
		if(inex.equals("0"))
		{
			char last=chk.charAt(chk.length()-1);
			if(last=='+'||last=='-'||last=='*'||last=='/')
			{
				exp.setText(chk.substring(0,chk.length()-1));
				return true;
			}
		}
		return false;
	}
	public static void main(String args[])
	{
		new Calc();
	}
}

class Calculate
{
	String exp[];
	int length;
	void setExpression(String ex)
	{
		String delimit="((?<=\\+)|(?=\\+)|(?<=-)|(?=-)|(?<=\\*)|(?=\\*)|(?<=/)|(?=/)|(?<=~)|(?=~))";
		exp=ex.split(String.format(delimit, ";"));
		length=exp.length;
	}
	String getResult()
	{
		int i=0,j=0;
		Vector<String> stk=new Vector<String>();
		String postfix[]=new String[length];
		while(i<length)
		{
			if(exp[i].equals("+")||exp[i].equals("-")||exp[i].equals("*")||exp[i].equals("/"))
			{
				while((stk.size()>=1)&&(getPriority(stk.elementAt(stk.size()-1))>getPriority(exp[i])))
				{
					postfix[j]=stk.elementAt(stk.size()-1);
					stk.removeElementAt(stk.size()-1);
					j++;
				}
				stk.add(exp[i]);
				i++;
			}
			else
			{
				postfix[j]=exp[i];
				i++;
				j++;
			}
		}
		while(stk.size()>=1)
		{
			postfix[j]=stk.elementAt(stk.size()-1);
			stk.removeElementAt(stk.size()-1);
			j++;
		}
		
		return evaluate(postfix);
	}
	int getPriority(String op)
	{
		if(op.equals("+")||op.equals("-"))
			return 0;
		else
			return 1;
	}
	String evaluate(String postfix[])
	{
		int i=0;
		length=postfix.length;
		String now=null;
		Vector<Double> stk=new Vector<Double>();
		double opnd1,opnd2,res=0;
		while(i<length)
		{
			now=postfix[i];
			if(isNumeric(now))
			{
				stk.add(Double.parseDouble(now));
			}
			else if(now.equals("~"))
			{
				i++;
				now=postfix[i];
				Double d=Double.parseDouble(now);
				d=d*-1;
				stk.add(d);
			}
			else
			{
				opnd2=stk.elementAt(stk.size()-1);
				stk.removeElementAt(stk.size()-1);
				opnd1=stk.elementAt(stk.size()-1);
				stk.removeElementAt(stk.size()-1);
				switch(now)
				{
					case "+":	res=opnd1+opnd2;
					break;
					case "-":	res=opnd1-opnd2;
					break;
					case "*":	res=opnd1*opnd2;
					break;
					case "/":
									res=opnd1/opnd2;
									if(Double.isNaN(res)||Double.isInfinite(res))
									{
										return "Invalid";
									}
					break;
				}
				stk.add(res);
			}
			i++;
		}
		res=stk.elementAt(stk.size()-1);
		stk.removeElementAt(stk.size()-1);
		now=Double.toString(res);
		if(res<0)
			now="~"+now.substring(1,now.length());
		return now;
	}
	public static boolean isNumeric(String str)
	{
		try
		{
			double d = Double.parseDouble(str);
		}
		catch(NumberFormatException nfe)
		{
			return false;
		}
  return true;  
}
}