Discussion1 Quiz

Q1 Which of the following are invalid Java identifiers (variable names)? a) if b) n4m3 c) Java d) e) DEFAULT_VALUE f) bad-choice g) 1two3 h) first name i) last.name

A1 Which of the following are invalid Java identifiers (variable names)? a) if b) n4m3 c) Java d) e) DEFAULT_VALUE f) bad-choice g) 1two3 h) first name i) last.name

Q2 Which of these identifiers violate the naming convention for object names? a) R2D2 b) isthisokay? c) Java d) 3CPO e) ThisIsReallyOkay f) Java g) anotherbadone

A2 Which of these identifiers violate the naming convention for object names? a) R2D2 b) isthisokay? c) Java d) 3CPO e) ThisIsReallyOkay f) Java g) anotherbadone

Q3 What is the output of the following statements a) System.out.println( (a++)++ ); b) System.out.println( 2.5 == 5 / 2 ); c) System.out.println( /2 ); d) System.out.println( 5 % 3); e) System.out.println(5 + 4/2.0); f) float f = 1.1; System.out.println(f – 0.1); g) int a = 10; System.out.println(a = 11);

A3 What is the output of the following statements a) System.out.println( (a++)++ ); //error! b) System.out.println( 2.5 == 5 / 2 ); //false c) System.out.println( /2 ); //3.0 d) System.out.println( 5 % 3); //2 e) System.out.println(5 + 4/2.0); // 7.0 f) float f = 1.1; System.out.println(f – 0.1); //error! g) int a = 10; System.out.println(a = 11); //11

Q4 What is the result? boolean b1 = true; Boolean b2 = false; System.out.println(b1 || b2 = true); System.out.println(b1); System.out.println(b2);

A4 What is the result? boolean b1 = true; Boolean b2 = false; System.out.println(b1 || b2 = true); //b1 || b2 is evaluated first before = System.out.println(b1); System.out.println(b2);

Q5 What is the result? boolean b1 = true; Boolean b2 = false; System.out.println(b1 || (b2 = true)); System.out.println(b1); System.out.println(b2);

A5 What is the result? boolean b1 = true; Boolean b2 = false; System.out.println(b1 || (b2 = true)); //true System.out.println(b1); //true System.out.println(b2); //false

Q6 What is the result? boolean b1 = true; Boolean b2 = false; System.out.println(b1 && (b2 = true)); System.out.println(b1); System.out.println(b2);

A6 What is the result? boolean b1 = true; Boolean b2 = false; System.out.println(b1 && (b2 = true)); //true System.out.println(b1); //true System.out.println(b2); //true

Q7 What’s the output? String s1 = new String("John"); String s2 = new String("John"); if (s1 == s2) System.out.println("s1 == s2 is true"); else System.out.println("s1 == s2 is false");

A7 What’s the output? String s1 = new String("John"); String s2 = new String("John"); if (s1 == s2) System.out.println("s1 == s2 is true"); else System.out.println("s1 == s2 is false"); // s1 == s2 is false

Q8 Is there any problem with this? int a = 10; double b = 1.0; a = a + b; System.out.println(a);

A8 Is there any problem with this? int a = 10; double b = 1.0; a = a + b; //type error System.out.println(a);

Q8 Is there any problem with this? int a = 10; double b = 1.0; a += b; System.out.println(a);

A8 Is there any problem with this? int a = 10; double b = 1.0; a += b; System.out.println(a); //no problem! lhs op= rhs is actually lhs op= (type of lhs)rhs