作用:防止不同的人写的类的名称相同冲突了,
package testPackage1.java;
class testPg {
public String talk(){
return "talk()";
}
}
class testAnother{
public static void main(String[] args){
System.out.println(new testPg().talk());
}
}
package name1.java;
public class Myhome {
public String city = "Beijing";
public void print(){
System.out.println(city);
}
}
package name2.java;
public class Myhome {
public String city = "Tianjin";
public void print(){
System.out.println(city);
}
}
import name1.java.*;
import name1.java.Myhome;
//import name2.java.Myhome; // 同名不能让你一起导入
class testImport {
public static void main(String[] args){
Myhome home1 = new Myhome();
home1.print();
name2.java.Myhome home2 = new name2.java.Myhome();
home2.print();
}
}
输出:
Beijing
Tianjin
java.lang
:包含一些Java核心类,String、Math、Integer、System、Thread,在 Java1.2 以后,java.lang
会被自动导入,不需要 importjava.awt
:抽象窗口工具,用来构建GUIjavax.swing
:轻量级GUI组件javax.net
:网络javax.io
:输入输出javax.util
:实用工具default
cmd :jar -cvf name_of_jar.jar targetPackage