多选题 Given:
42. String s1 = " ";
43. StringBuffer s2 = new StringBuffer(" ");
44. StringBuilder s3 = new StringBuilder(" ");
45. for(int i = 0; i ＜ 1000; i++) // Loop #1
46. s1 = s1.concat("a");
47. for(int i = 0; i ＜ 1000; i++) // Loop #2
48. s2. append ("a");
49. for(int i = 0; i ＜ i000; i++) // Loop #3
50. s3. append ("a");
Which statements will typically be true? (Choose all that apply.)

A、 Compilation fails.
B、 Loop #3 will tend to execute faster than Loop #2.
C、 Loop #1 will tend to use less memory than the other two loops.
D、 Loop #1 will tend to use more memory than the other two loops.
E、 All three loops will tend to use about the same amount of memory.
F、 In order for this code to compile, the java.util package is required.
G、 If multiple threads need to use an object, the s2 object should be safer than the s3 object.

【正确答案】 B、D、G

【答案解析】