'javac' - The Java Compiler

Part:   1  2  3  4   5  6 

(Continued from previous part...)

Test 2 - Storing PackagedHello.java in the right directory:

>mkdir .\com
>mkdir .\com\herong
>mkdir .\com\herong\util

>copy PackagedHello.java .\com\herong\util

>del PackagedHell.*

>javac .\com\herong\util\PackagedHello.java

>dir .\com\herong\util
   459 PackagedHello.class
   264 PackagedHello.java

>java -cp . com.herong.util.PackagedHello
Packaged: Hello world!

As you can see, the compiler outputs the class file in the same directory as the source file.

Test 3 - Outputing PackagedHello.class to a new directory:

>mkdir .\cls

>javac -d .\cls .\com\herong\util\PackagedHello.java

>dir .\cls\com\herong\util
   459 PackagedHello.class

>java -cp .\cls com.herong.util.PackagedHello
Packaged: Hello world!

This time, the compiler outputs the class file under a directory path: .\cls.

"import" Statements

Java offers two types of "import" statements:

1. Single Type Import: "import TypeName;" - It loads the definition of a single type immediately from the specified package.

2. On-Demand Type Import: "import PackageName.*;" - It tells JVM to search this package for any missing type.

"javac" command processes there two different types of "import" statements differently. I wrote the following 4 source files.

1. ClsA.java:

/**
 * ClsA.java
 * Copyright (c) 2006 by Dr. Herong Yang, http://www.herongyang.com/
 */
package com.herong.util;
public class ClsA {
   public void printInfo() {
      System.out.println("Class: com.herong.util.ClsA");
   }
}

2. ClsB.java:

/**
 * ClsB.java
 * Copyright (c) 2006 by Dr. Herong Yang, http://www.herongyang.com/
 */
package com.herong.util;
public class ClsB {
   public void printInfo() {
      System.out.println("Class: com.herong.util.ClsB");
   }
}

3. ImportTestA.java:

/**
 * ImportTestA.java
 * Copyright (c) 2006 by Dr. Herong Yang, http://www.herongyang.com/
 */
import com.herong.util.*;
public class ImportTestA {
   public static void main(String[] arg){
      ClsA a = new ClsA();
      a.printInfo();
      ClsB b = new ClsB();
      b.printInfo();
   }
}

(Continued on next part...)

Part:   1  2  3  4   5  6