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Here is the source code:
import java.applet.*;
import java.awt.*;
public class PrimeTest extends Applet
{
boolean isPrime = true;
long testedValue = 2;
long divisor = 1;
TextField theTextField;
// Standard Applet procedures
public void init()
{
setLayout(new FlowLayout(FlowLayout.LEFT));
theTextField = new TextField("2", 19);
add(new Label("Number to test:"));
add(theTextField);
add(new Button("Check for primality"));
}
public boolean action(Event evt, Object arg)
{
if ( evt.target instanceof Button )
DoTest();
return true;
}
public void paint(Graphics g)
{
g.clearRect(0, 50, 200, 80);
if ( isPrime )
g.drawString("" + testedValue + " is prime", 10, 60);
else
g.drawString("" + testedValue + " is divisible by " + divisor, 10, 60);
}
// Procedures specific to Primes
public void DoTest()
{
String numString;
long testPrime;
numString = theTextField.getText();
testPrime = Long.parseLong(numString);
if ( testPrime < 2 )
return /* nothing */ ;
divisor = IsPrime(testPrime);
if ( divisor == testPrime )
isPrime = true;
else
isPrime = false;
testedValue = testPrime;
repaint();
}
public long IsPrime(long testPrime)
{
long test;
// should at least use square root
test = 2;
while ( test < testPrime )
{
if ( testPrime % test == 0 )
return test;
if ( test == 2 )
test++;
else
test += 2;
}
return testPrime;
}
}
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