Two Types of "import" Statements

Java Tools Tutorials - Herong's Tutorial Examples

∟Two Types of "import" Statements

This section describes two types of 'import' statements: Single Type Import and On-Demand Type Import. 4 sample Java source files are provided to test 'import' statements.

Java offers two types of "import" statements:

1. Single Type Import: "import type_name;" - It tells JVM to load the definition of a single type immediately from the specified package.

2. On-Demand Type Import: "import package_name.*;" - It tells JVM to search the specified package for any missing type when it is needed.

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

1. ClsA.java:

/* ClsA.java
 * Copyright (c) 2005 HerongYang.com. All Rights Reserved.
 */
package com.herongyang.util;
public class ClsA {
   public void printInfo() {
      System.out.println("Class: com.herongyang.util.ClsA");
   }
}

2. ClsB.java:

/* ClsB.java
 * Copyright (c) 2005 HerongYang.com. All Rights Reserved.
 */
package com.herongyang.util;
public class ClsB {
   public void printInfo() {
      System.out.println("Class: com.herongyang.util.ClsB");
   }
}

3. ImportTestA.java:

/* ImportTestA.java
 * Copyright (c) 2005 HerongYang.com. All Rights Reserved.
 */
import com.herongyang.util.*;
public class ImportTestA {
   public static void main(String[] arg){
      ClsA a = new ClsA();
      a.printInfo();
      ClsB b = new ClsB();
      b.printInfo();
   }
}

4. ImportTestB.java:

/* ImportTestB.java
 * Copyright (c) 2005 HerongYang.com. All Rights Reserved.
 */
import com.herongyang.util.ClsA;
import com.herongyang.util.ClsB;
public class ImportTestB {
   public static void main(String[] arg){
      ClsA a = new ClsA();
      a.printInfo();
      ClsB b = new ClsB();
      b.printInfo();
   }
}