/*
  \ch3\Decision.java
*/
class Decision
{
 public static void main(String [] args)
 {
  int x;
  int y;
  x=10;
  y=20;
  if(x==y)
  System.out.println("x等于y.");
  if(x<y)
  System.out.println("x小于y.");
 }
}

/*
  \ch3\Iteration.java
*/
class Iteration
{
 public static void main(String [] args)
 {
  for(int i=1;i<10;i++)
  System.out.println("i等于"+i);
 }
}

 

import javax.swing.JOptionPane;
class TryCatchFinally
{
 public static void main(String [] args)
 {
  int wheels;
  int mirrors;
  String strWheels;
  try
  {
   strWheels=JOptionPane.showInputDialog("请输入轮子的数目");
   wheels=Integer.parseInt(strWheels);
  }
  catch(Exception e)
  {
   System.out.println("输入值错误!");
  }
  finally
  {
   wheels=4;
  }
  JOptionPane.showMessageDialog(null,"车子共有轮子"+wheels+"个","黄聪明提醒你……",JOptionPane.INFORMATION_MESSAGE);
  mirrors=wheels/2;
  JOptionPane.showMessageDialog(null,"车子共有镜子"+mirrors+"个","黄聪明提醒你……",JOptionPane.INFORMATION_MESSAGE);
    System.exit(0);
  }
}

 

/*
   \ch3\Application.java
*/
class Circle
{
 double radius;
 void setRadius(double radius)
 {
  this.radius=radius;
 }
 void showRadius()
 {
  System.out.println("半径"+radius);
  return;
 }
 double getArea()
 {
  return Math.PI*Math.pow(radius,2);
 }
}
class Application
{
 public static void main(String [] args)
 {
  Circle aCircle;
  aCircle=new Circle();
  aCircle.setRadius(12.0);
  aCircle.showRadius();
  System.out.println("aCircle 的面积等于"+aCircle.getArea());
 }
}

 

/*
   \ch3\Application2.java
*/
class Person
{
 String m_name;
 boolean m_gender;
 void name()
 {
  System.out.println("姓名-->"+m_name);
 }
 void gender()
 {
  System.out.println("姓别-->"+m_gender);
 }
 void name(String name)
 {
  m_name=name;
 }
 void gender(boolean gender)
 {
  m_gender=gender;
 }
}
class Student extends Person
{
 String m_ID;
 void ID()
 {
  System.out.println("学号-->"+m_ID);
 }
 void ID(String ID)
 {
  m_ID=ID;
 }
}
class Application2
{
 public static void main(String [] args)
 {
  Student John=new Student();
  John.name("John");
  John.gender(true);
  John.ID("123456");
  John.name();
  John.gender();
  John.ID();
 }
}

 

本文来源：http://blog.csdn.net/flyever581549/archive/2007/08/19/1750493.aspx