《Java参考大全》之二

 1、

/*
 This is a simple java program.
 Call this file "Example.java".
 */
 class Example{
  //Your program begins with a call to main().
  public static void main(String args[]){
 System.out.println("This is a simple Java program.");
  }
 }

2、

/*
   Here is another short example.
   Call this file "Example2.java".
 */
 class Example2 {
  public static void main(String args[]) {
   int num;//this declares a variable called num
   num=100;//this assigns num the value 100
   System.out.println("This is num:" + num);
   num=num*2;
   System.out.print("This value of num*2 is ");
   System.out.println(num);
  }
 }

3、

/*
  Demonstrate the if.
  Call this file "IfSample.java".
 */
 class IfSample {
  public static void main(String args[]) {
  int x,y;
  x=10;
  y=20;
  if(x<y)System.out.println("x is less than y");
 
  x=x*2;
  if(x==y) System.out.println("x now equal to y");
 
  x=x*2;
  if(x>y) System.out.println("x now equal to y");
  //this won't display anything
  if(x==y) System.out.println("you won't see this");
  }
 }

4、

/*
 Demonstrate the for loop.
 Call this file "ForTest.java".
*/
class ForTest {
      public static void main(String args[]){
       int x;
        for (x=0;x<10;x=x+1)
  System.out.println("This is x:"+x);
 }
}

5、

/*
 Demonstrate a block of code.
 Call this file "BlockTest.java"
*/
class BlockTest {
 public static void main(String args[]){
  int x,y;
  y=20;
  //the target of this loop is a block
  for(x=0;x<10;x++){
 
      System.out.println("This is x:"+x);
      System.out.println("This is y:"+y);
      y=y-2;
  }   
 }
}