package是Java产生包路径的关键字,且应放在程序的第一句;
同一个包中的类在引用时,不需要import语句,不同包引用时需要添加import语句,且需要改变类的权限和类中数据成员为public类型;
//该类在包 RunFighterPlane中
package RunFighterPlane;
class FighterPlane
{ String name;
int missileNum;
void fire(){
if (missileNum>0){
System.out.println("now fire a missile !");
missileNum -= 1;
}
else{
System.out.println("No missile left !");
}
}
}
//该类在包 RunFighterPlane中
package RunFighterPlane;
public class RunPlane
{
public static void main(String args[]){
FighterPlane fp = new FighterPlane();
fp.name = "苏35";
fp.missileNum = 6;
fp.fire();
}
}//该类在包Resource中
package Resource;
public class FighterPlane
{
public String name;
public int missileNum;
public void fire(){
if (missileNum>0){
System.out.println("now fire a missile !");
missileNum -= 1;
}
else{
System.out.println("No missile left !");
}
}
}//该类在包run中
package run;
import Resource.*;
public class RunPlane
{
public static void main(String args[]){
FighterPlane fp = new FighterPlane();
fp.name = "苏35";
fp.missileNum = 6;
fp.fire();
}
}
类处于包的情况如下图:
运行结果: