// Primes.java
// Find all primes up to user-specified limit.

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


public class Primes extends JApplet {

    JTextField testNumField;
    JLabel primeLabel;
    JTextField firstNField;
    JTextField countField;
    JTextArea listArea;


    public void init() {
	JLabel testNumLabel;
	JLabel firstNLabel;
	JLabel countLabel;

	Container container = getContentPane();
	int panelRowsSize = 3;
	container.setLayout( new GridLayout( panelRowsSize, 1 ) );
	//container.setLayout( new FlowLayout( ) );

	JPanel [] panelRows = new JPanel[panelRowsSize];
	for (int i=0; i<panelRowsSize; i++) {
	    panelRows[i] = new JPanel();
	    panelRows[i].setLayout( new FlowLayout() );
	    container.add( panelRows[i] );
	}

	Font bigFont = new Font( "Monospaced", Font.BOLD, 16 );
        
	testNumLabel = new JLabel( "Number to test" );
	testNumLabel.setFont( bigFont );
	panelRows[0].add( testNumLabel );

	testNumField = new JTextField( 12 );
	testNumField.setFont( bigFont );
	panelRows[0].add( testNumField );

	primeLabel = new JLabel( "        " );
	primeLabel.setFont( bigFont );
	panelRows[0].add( primeLabel );


	firstNLabel = new JLabel( "Primes less than" );
	firstNLabel.setFont( bigFont );
	panelRows[1].add( firstNLabel );

	firstNField = new JTextField( 5 );
	firstNField.setFont( bigFont );
	panelRows[1].add( firstNField );

	countLabel = new JLabel( "Count" );
	countLabel.setFont( bigFont );
	panelRows[1].add( countLabel );

	countField = new JTextField( 5 );
	countField.setEditable( false );
	countField.setFont( bigFont );
	panelRows[1].add( countField );

	listArea = new JTextArea( 10, 30 );
	Font smallFont = new Font( "Monospaced", Font.BOLD, 12 );
	listArea.setFont( smallFont );
	JScrollPane listScroll = new JScrollPane( listArea );
	panelRows[2].add( listScroll );


	testNumField.addActionListener( 
        	new ActionListener () {
		    public void actionPerformed( ActionEvent event ) {
			long num=0;
			try {
			    num = Long.parseLong( testNumField.getText() );
			}
			catch (NumberFormatException e) {
			    testNumField.setText( "integer please" );
			}
			if ( num <= 0 )
			    testNumField.setText( "positive please" );
			else
			    if ( isPrime( num ) )
				primeLabel.setText( "is prime" );
			    else
				primeLabel.setText( "is not prime" );
		    }
		}
		);


	firstNField.addActionListener( 
        	new ActionListener () {
		    public void actionPerformed( ActionEvent event ) {
			long limit=0;
			try {
			    limit = Long.parseLong( firstNField.getText() );
			}
			catch (NumberFormatException e) {
			    firstNField.setText( "integer please" );
			}
			if ( limit <= 0 )
			    firstNField.setText( "positive please" );
			else {

			    int count=0;
			    String result="";
			    listArea.setText( "" );
	
			    for (int i=2; i<=limit; i++)
				if ( isPrime( i ) ) {
				    result += " " + i;
				    count++;
				    if (count%5 == 0)
					result += "\n";
				}
			    listArea.setText( result );
			    countField.setText( "" + count );
			}
		    }
		}
		);

    }


    public void start() {
	testNumField.requestFocusInWindow();
    }


    boolean isPrime (long num) {
	
	long i;
	long limit = (long)Math.sqrt( num );

	//not the best way.  should try to divide by primes only...
	for (i=2; i<=limit; i++)
	    if (num%i == 0)
		break;		// evenly divisible
	
	if (i <= limit)
	    return false;
	else
	    return true;
    }
}






/*
    public void init() {
	table = new HashMap();

	Container container = getContentPane();
	int panelRowsSize = 3;
	//container.setLayout( new GridLayout( panelRowsSize, 1 ) );
	container.setLayout( new FlowLayout( ) );

	JPanel [] panelRows = new JPanel[panelRowsSize];
	for (int i=0; i<panelRowsSize; i++) {
	    panelRows[i] = new JPanel();
	    panelRows[i].setLayout( new FlowLayout() );
	    container.add( panelRows[i] );
	}

	JLabel inputLabel = new JLabel( "Enter boolean expression" );
	panelRows[0].add( inputLabel );

	inputField = new JTextField( 20 );
	panelRows[0].add( inputField );
	inputField.addActionListener( 
        	new ActionListener () {
		    public void actionPerformed( ActionEvent event ) {
			
			table.clear();
			errorLabel.setText( "" );
			//resultLabel.setText( "" );
			ttArea.setText( "" );
			input = inputField.getText();			


			Set vars = new TreeSet(); //sorted p q r etc.
			int num_vars=0;
			//find the variables of the expression.
			index = 0;
			while ( index < input.length() ) {
			    if ( Character.isLetter( input.charAt( index ) ) ){

				String c = new String(""+input.charAt( index ));
				if ( ! vars.contains( c ) ) { 
				    
				    vars.add( c );      
				    num_vars++;
				    //ttArea.append( "   " + c );
				}
			    }
			    index++;
			}
			
			Iterator iter = vars.iterator();
			while ( iter.hasNext() ) 
			    ttArea.append( "   " + (String)iter.next() );
			ttArea.append( "\n" );

			

			//for each truth combination (i.e. each row of TT)
			for (int row=0; row<(1<<num_vars); row++) {

			    //use binary value of row for truth values of variables
			    int var_num_shift=num_vars-1;  //shift amount

			    iter = vars.iterator();
			    while ( iter.hasNext() ) {
				Boolean b;
				if ( ((row>>var_num_shift) & 1) == 0 )
				    b = Boolean.valueOf( false );
				else 
				    b = Boolean.valueOf( true );

				table.put( (String)iter.next(), b );

				ttArea.append("   " + ((row>>var_num_shift)&1));
				var_num_shift--;
			    }

			    ttArea.append( "    " ); 




			    index = 0;

			    
			    while ( index < input.length() ) {
				get_token();
				if (curr_tok == END)
				    break;
				if (curr_tok == PRINT)
				    continue;
				ttArea.append( expr( false ) + "\n" );
			    }
			}
			
			
		    }
		}
		);

	ttArea = new JTextArea( 10, 20 );
	JScrollPane ttScroll = new JScrollPane( ttArea );
	panelRows[1].add( ttScroll );


	clearButton = new JButton( "Clear" );
	panelRows[2].add( clearButton );
	clearButton.addActionListener( 
        	new ActionListener () {
		    public void actionPerformed( ActionEvent event ) {
			inputField.setText( "" );
			errorLabel.setText( "" );
			ttArea.setText( "" );
			inputField.requestFocusInWindow();
		    }
		}
		);

	errorLabel = new JLabel( "" );
	panelRows[2].add( errorLabel );
    }




*/