class Tank{
int level;
String msg;
Tmp tmp;
@Override
public String toString() {
return "level = "+level+" msg="+msg+" tmp="+tmp;
}
}
class Tmp{
private String name;
public Tmp(String name){
this.name=name;
}
@Override
public String toString() {
return this.name;
}
}
-----------------
Tank t1 = new Tank();
t1.level =1;
t1.msg="message 1";
t1.tmp = new Tmp("tmp 1");
System.out.println(t1);
Tank t2 = new Tank();
t2.level =2;
t2.msg="message 2";
t2.tmp = new Tmp("tmp 2");
System.out.println(t2);
t1 = t2 ;
t2賦值給t1后，t2中原對象的引用也指向了t1對象的引用，原先t2對象的引用被覆蓋，信息丟失。
此時t2與t1指向同一個引用。