Mouse.java

import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
public class Retta extends JPanel implements MouseListener{
private int x1;
private int Y1;
private int x2;
private int y2;
private int conta=0;
public void mouseClicked(MouseEvent e){
int x=e.getX();
int y=e.getY();
conta++;
if(conta==1){
x1=x;
y1=y;
}
if(conta==2){
x2=x;
y2=y;
conta=0;
repaint();
}
}
public void mouseEntered(MouseEvent e){}
public void mouseExited(MouseEvent e){}
public void mousePressed(MouseEvent e){}
public void mouseReleased(MouseEvent e){}
public void paintComponent(Graphics g){
g.drawLine(x1,y1,x2,y2);
}
}

Conta lettere

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class Conta {
JFrame f1=new JFrame("Conta le lettere");
JButton b1=new JButton("Vai");
JLabel r1=new JLabel("qui verra visualizzato il risultato");
JTextField t1=new JTextField("casa");
JTextField t2= new JTextField("inserisci qui la lettera da cercare ");
String s2;
String inserita="a";
JPanel p=new JPanel();

public Conta(){
f1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f1.setSize(500,500);
b1.addActionListener(new Ascoltatore());
f1.add(BorderLayout.NORTH,t1);
p.add(BorderLayout.WEST,b1);
t2.setSize(300, 30);
p.add(BorderLayout.CENTER,t2);
p.add(BorderLayout.EAST,r1);
f1.add(BorderLayout.CENTER,p);
f1.setVisible(true);
}
public int cerca(String s1,String inserita){
int x=0;
for(int i=0;i s2=s1.substring(i,i+1);
if(s2.equals(inserita)){
x++;
}
}
return x;
}

class Ascoltatore implements ActionListener{
public void actionPerformed(ActionEvent e){
String testo1=t1.getText();
String testo2=t2.getText();
int risultato=cerca(testo1,testo2);
String risultato2=Integer.toString(risultato);
r1.setText("la lettera è stata trovata:"+risultato2+" volte");
f1.repaint();
}
}

public static void main(String Args[]){
Conta c=new Conta();

}
}