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();   (A), (C) & (E)   (A), (D) & (E)   (A), (B) & (C)   (D) & (E)   (C), (D) & (E)   Hint Half-n-half Clue   2. The methods wait() and notify() are defined in   java.lang.Thread   java.lang.String   java.lang.ThreadGroup   java.lang.Object   java.lang.Runnable   Half-n-half Clue   3. What will be the content of array variable table after executing the following code? for(int i = 0; i < 3; i + +) for(int j = 0; j < 3; j + +) if(j = i) table[i][j] = 1; else table[i][j] = 0;   0 0 1 0 1 0 1 0 0   1 0 0 0 1 0 0 0 1   0 0 0 0 0 0 0 0 0   1 0 0 1 1 0 1 1 1   Half-n-half Clue   4. Given the code String s1 = "yes"; String s2 = "yes"; String s3 = new String(s1); Which of the following would equate to true? (A) s1 == s2 (B) s1 = s2 (C) s3 == s1 (D) s1.equals(s2) (E) s3.equals(s1)   (C), (D) & (E)   (A), (B) & (C)   (D) & (E)   (A), (D) & (E)   (A), (C) & (E)   Half-n-half Clue   5. Consider the following code int number[] = new int[5]; After execution of this statement, which of the following are true? (A) number[0] is undefined (B) number[5] is undefined (C) number[4] is null (D) number[2] is 0 (E) number.length() is 5   (C) & (E)   (B), (D) & (E)   (E)   (A) & (E)   Half-n-half Clue   6. Which of the following methods belong to the String class?   substring()   All of these   equals()   length()   compareTo()   None of these   Half-n-half Clue   7. Given the following code: class Base { int x = 10; } class Derived extends Base { int x = 20; } Base b = new Base(); Derived d = new Derived ( ); Base bd = new Derived(); The statement System.out.println(b.x + " " + d.x + " " + bd.x); will produce the output   10 20 10   20 10 20   10 20 20   20 20 10   Half-n-half Clue