赋值操作后，对象的引用发生变化

// 此用例来源于Thinking in java 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; }}

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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赋值给t1后，t2中原对象的引用也指向了t1对象的引用，原先t2对象的引用被覆盖，信息丢失。
此时t2与t1指向同一个引用。