整理

一、消息框

import javax.swing.JOptionPane;  // import class JOptionPane

public class Welcome2 {
   public static void main( String args[] )
   {
      JOptionPane.showMessageDialog(
         null, "Welcome
to
Java
Programming!" );

      System.exit( 0 );  // terminate the program
   }
}

二、接受参数，取值

public class JavaAppArguments {
    public static void main(String[] args) {
                System.out.println("参数个数："+args.length);
for (String arg : args) {
                    System.out.println(arg);}
}
}

三、double精度损失

public class TestDouble {

    public static void main(String args[]) {
        System.out.println("0.05 + 0.01 = " + (0.05 + 0.01));
        System.out.println("1.0 - 0.42 = " + (1.0 - 0.42));
        System.out.println("4.015 * 100 = " + (4.015 * 100));
        System.out.println("123.3 / 100 = " + (123.3 / 100));
    }
}

四、输出

public class TestDouble {

    public static void main(String args[]) {
        int X=100;
        int Y=200;
        System.out.println("X+Y="+X+Y);
        System.out.println(X+Y+"=X+Y");

    }
}