java編程思想_005別名現象

package wzs.test2;//將一個對象賦值給另一個對象，實際是將引用從一個地方複製到另一個地方//這意味著，如果對象tank1=tank2，那麼tank1和tank2都指向原本只有tank2指向的那個對象//為了避免這種問題，應該tank1.level=tank2.levelpublic class Test_wzs2{    public static void main(String[] args)    {        Tank tank1 = new Tank();        Tank tank2 = new Tank();        tank1.level = 1;        tank2.level = 2;        System.out.println("tank1.level=" + tank1.level + ", tank2.level=" + tank2.level);        tank1 = tank2;        System.out.println("tank1.level=" + tank1.level + ", tank2.level=" + tank2.level);        tank1.level = 5;        System.out.println("tank1.level=" + tank1.level + ", tank2.level=" + tank2.level);        tank2.level = 7;        System.out.println("tank1.level=" + tank1.level + ", tank2.level=" + tank2.level);        // ----------------------------        Tank tank3 = new Tank();        Tank tank4 = new Tank();        tank3.level = 1;        tank4.level = 2;        tank3.level = tank4.level;        System.out.println("\ntank3.level=" + tank3.level + ", tank4.level=" + tank4.level);        tank3.level = 7;        tank4.level = 8;        System.out.println("tank3.level=" + tank3.level + ", tank4.level=" + tank4.level);    }}class Tank{    int level;}

輸出結果:

tank1.level=1, tank2.level=2tank1.level=2, tank2.level=2tank1.level=5, tank2.level=5tank1.level=7, tank2.level=7tank3.level=2, tank4.level=2tank3.level=7, tank4.level=8