1. Suppose that s1 and s2 are two strings. Which of the statements or expressions are valid? (A) String s3 = s1 + s2; (B) String s3 = s1 - s2; (C) s1 <= s2 (D) s1.compareTo(s2); (E) int m = s1.length();   (C), (D) & (E)   (A), (C) & (E)   (A), (B) & (C)   (A), (D) & (E)   (D) & (E)   Hint Half-n-half Clue   2. Which of the following methods belong to the String class?   All of these   substring()   length()   compareTo()   equals()   None of these   Half-n-half Clue   3. Given the code String s = new String("abc"); Which of the following calls are valid? (A) s.trim() (B) s.replace('a', 'A') (C) s.substring(3) (D) s.toUppercase() (E) s.setCharAt(1,'A') (F) s.append("xyz")   (A), (B), (C) & (D)   (C), (D) & (E)   (A), (B) & (C)   (D) & (E)   (A), (C), (D) & (E)   Half-n-half Clue   4. Which of the following classes are available in the java.lang package? (A) Stack (B) Object (C) Math (D) Random (E) String (F) StringBuffer (G) Vector   (A), (B), (C), (E) & (F)   (B), (C), (E) & (F)   (C), (E) & (F)   (B), (E) & (F)   (B), (C) & (E)   Half-n-half Clue   5. Which of the following statements are valid array declaration? (A) int number(); (B) float average[]; (C) double[] marks; (D) counter int[];   (D)   (A) & (C)   (A)   (B) & (C)   Half-n-half Clue   6. The methods wait() and notify() are defined in   java.lang.Object   java.lang.Runnable   java.lang.Thread   java.lang.ThreadGroup   java.lang.String   Half-n-half Clue   7. Which of the following statements are true? (A) A Java monitor must either extend Thread or implement Runnable. (B) The sleep() method should be enclosed in try ... catch block. (C) The yield() method should be enclosed in try ... catch block. (D) A thread can be temporarily suspended from running by using the wait() method. (E) A suspended thread using suspend() method can be revived using the resume() method.   (B), (D) & (E)   (A), (B), (D) & (E)   (A), (B) & (D)   (D) & (E)   (C), (D) & (E)   Half-n-half Clue