QUESTION 1

QUESTION 1 
Given: 
 
1. public class KungFu { 
2.     public static void main(String[] args) { 
3.         Integer x = 400; 
4.         Integer y = x; 
5.         x++; 
6.         StringBuilder sb1 = new StringBuilder("123"); 
7.         StringBuilder sb2 = sb1; 
8.         sb1.append("5"); 
9.         System.out.println((x == y) + " " + (sb1 == sb2)); 
10.     } 
11. } 
 
What is the result? 
 
A. true true 
B. false true 
C. true false 
D. false false 
E. Compilation fails. 
F. An exception is thrown at runtime. 
Solution : B 

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plus imformation 

x++ 이므로 y에 x값 대입후 x값은 +1 증가된 상태 --> false 

Stringbuilder.append = 인스턴스에 append ( 문자열 ) 추가 --> True