对于下列代码：理由publicclassSample{longlength;publicSample(longl){length=l;}publicstaticvoidmain(Stringarg[]){Samples1,s2,s3;s1=newSample(21L);s2=newSample(21L);s3=s2;longm=21L;}}下列哪些表达式返回

Question

对于下列代码：理由
publicclass Sample{
long length;
public Sample(long l){ length =l; }
public static void main(Stringarg[]){
Sample s1,s2,s3;
s1 = new Sample(21L);
s2 = new Sample(21L);
s3 = s2;
long m = 21L;
}
}
下列哪些表达式返回值为'true'?
A s1 = = s2;
B s2 = = s3;
C m = = s1;
D s1.equals(m)

Answer 1

A s1、s2是两个不同的对象,也就是地址不一样 返回值false
B s2 = = s3 s3是对s2的引用,或称赋值,所以相等,返回true
C m和s1的类型不同 编译器提示出错
D 类型不同的两个对象比较肯定不相等,返回false
综上,选B