对于引用数据类型之间进行equals比较,在没有覆写equals方法的情况下,他们之间的比较还是基于他们在内存中的存放位置的地址值的,因为Object的equals方法也是用双等号(==)进行比较的,所以比较后的结果跟双等号(==)的结果相同。
Object中的equals()方法
publicbooleanequals(Objectobj){ return(this==obj); } 举个实例: packageorg.java.test; publicclassPerson{ privateintage; privateStringname; publicintgetAge(){ returnage; } publicvoidsetAge(intage){ this.age=age; } publicStringgetName(){ returnname; } publicvoidsetName(Stringname){ this.name=name; } publicPerson(intage,Stringname){ this.age=age; this.name=name; } publicPerson(){ } @Override publicinthashCode(){ finalintprime=31; intresult=1; result=prime*result+age; result=prime*result+((name==null)?0:name.hashCode()); returnresult; } @Override publicbooleanequals(Objectobj){ if(this==obj) returntrue; if(obj==null) returnfalse; if(getClass()!=obj.getClass()) returnfalse; Personother=(Person)obj; if(age!=other.age) returnfalse; if(name==null){ if(other.name!=null) returnfalse; }elseif(!name.equals(other.name)) returnfalse; returntrue; } } MainTest.java[java]view plaincopyprint? packageorg.java.test; publicclassMainTest{ publicstaticvoidmain(String[]args){ Personp1=newPerson(99,"A"); Personp2=newPerson(99,"A"); Personp3=p1; System.out.println(p1==p2);//false System.out.println(p1==p3);//true System.out.println(p1.equals(p2)); //未重写equals()方法,返回false //重写equals()方法后,比较的是内容,返回true; System.out.println("<====================>"); Strings1="hello"; Strings2="hello"; Strings3=newString("hello"); System.out.println(s1==s2);//true System.out.println(s1==s3);//false System.out.println(s1.equals(s2));//true System.out.println(s1.equals(s3));//true } }