hi: i need help with this programm, i need it to make calculations as a normal calc

Code :
import java.awt.*;
import java.awt.Color.*;
import java.awt.TextField.*;
import java.awt.event.*;
public class Calculator extends WindowAdapter
{
	//declaraion of variable types
	Frame f;
	TextField tf;
 
	Button  b1,b2,b3,b4,b5,b6,b7,b8,b9,b10,b11,b12,b13,b14,b15,b16;
	Panel west, center;
 
	public void makeCALC()
	{
		f = new Frame("Calculate it");
		tf = new TextField("0.0");
 
//assigning values to buttons
		b1 = new Button("7");
		b2 = new Button("8");
		b3 = new Button("9");
		b4 = new Button("/");
		b5 = new Button("4");
		b6 = new Button("5");
		b7 = new Button("6");
		b8 = new Button("*");
		b9 = new Button("1");
		b10 = new Button("2");
		b11 = new Button("3");
		b12 = new Button("-");
		b13 = new Button("0");
		b14 = new Button("=");
		b15 = new Button(".");
		b16 = new Button("+");
//setting up alignment and layout of grid
		west = new Panel();
		center = new Panel();
		center.setLayout(new GridLayout(4,4));
		f.add(tf,BorderLayout.NORTH);
		f.add(west,BorderLayout.WEST);
		f.add(center,BorderLayout.CENTER);
 
		center.add(b1);
		center.add(b2);
		center.add(b3);
		center.add(b4);
		center.add(b5);
		center.add(b6);
		center.add(b7);
		center.add(b8);
		center.add(b9);
		center.add(b10);
		center.add(b11);
		center.add(b12);
		center.add(b13);
		center.add(b14);
		center.add(b15);
		center.add(b16);
		f.setSize(500,500);
		f.setVisible(true);
 
//formating of font and color of numbers
		Font font = new Font("Verdana", Font.BOLD,40);
		f.setFont(font);
		b1.setForeground(Color.BLUE);
		b2.setForeground(Color.YELLOW);
		b3.setForeground(Color.DARK_GRAY);
		b4.setForeground(Color.RED);
		b5.setForeground(Color.GREEN);
		b6.setForeground(Color.CYAN);
		b7.setForeground(Color.LIGHT_GRAY);
		b8.setForeground(Color.ORANGE);
		b9.setForeground(Color.RED);
		b10.setForeground(Color.PINK);
		b11.setForeground(Color.GRAY);
		b12.setForeground(Color.MAGENTA);
		b13.setForeground(Color.WHITE);
		b14.setForeground(Color.YELLOW);
		b15.setForeground(Color.ORANGE);
		b16.setForeground(Color.PINK);
 
//method caller for buttons and frame
		f.addWindowListener(this);
		b1.addActionListener(new MyButtonHandler());
		b2.addActionListener(new MyButtonHandler());
		b3.addActionListener(new MyButtonHandler());
		b4.addActionListener(new MyButtonHandler());
		b5.addActionListener(new MyButtonHandler());
		b6.addActionListener(new MyButtonHandler());
		b7.addActionListener(new MyButtonHandler());
		b8.addActionListener(new MyButtonHandler());
		b9.addActionListener(new MyButtonHandler());
		b10.addActionListener(new MyButtonHandler());
		b11.addActionListener(new MyButtonHandler());
		b12.addActionListener(new MyButtonHandler());
		b13.addActionListener(new MyButtonHandler());
		b14.addActionListener(new MyButtonHandler());
		b15.addActionListener(new MyButtonHandler());
		b16.addActionListener(new MyButtonHandler());
 
 
}
//calling method to allow window to close
 
	public void windowClosing(WindowEvent we)
	{
		System.exit(0);
}
	public class MyButtonHandler implements ActionListener
	{
		public void actionPerformed(ActionEvent ae)
		{
//method to test values of label stored in button
			String label = ae.getActionCommand();
 
			if(label == "7")
			{
				tf.setText("7");
			}
			else if(label == "8")
			{
				tf.setText("8");
 
			}
			if(label == "9")
			{
				tf.setText("9");
			}
			else if(label == "/")
			{
				tf.setText("/");
			}
			if(label == "4")
			{
				tf.setText("4");
			}
			else if(label == "5")
			{
			tf.setText("5");
 
			}
			if(label == "6")
			{
			tf.setText("6");
			}
			else if(label == "*")
			{
			tf.setText("*");
 
			}
			else if(label == "1")
			{
				tf.setText("1");
			}
			else if(label == "2")
			{
				tf.setText("2");
			}
			else if(label == "3")
			{
				tf.setText("3");
			}
			else if(label == "-")
			{
				tf.setText("-");
			}
			else if(label == "0")
			{
				tf.setText("0");
			}
			else if(label == "=")
			{
				tf.setText("=");
			}
			else if(label == ".")
			{
				tf.setText(".");
			}
			else if(label == "+")
			{
				tf.setText("+");
			}
 
			else if(label == "Clear")
			{
				tf.setText("  ");
	}
		}
		}//end makeGUI()
		public static void main(String args[])
		{
			Calculator theNew = new Calculator();
			theNew.makeCALC();
 
	}
}