Practice · Characters, Strings, and Console Input

Q1

Which escape sequence moves the cursor to the next line?

A \t B \n C \r D \b

Q2

How do you place a double quote inside a string literal?

A "" B \" C '"' D It is impossible.

Q3

What is the output of System.out.println("A\tB\nC");?

A A B C on one line B A, a tab, B, then C on the next line C A\tB\nC literally D It does not compile.

Q4

Which declaration stores a single character?

A String c = 'A'; B char c = "A"; C char c = 'A'; D char c = A;

Q5

What is the value of '5' - '0'?

A 0 B 5 C '5' D It does not compile.

Q6

Which comparison is true?

A 'a' < 'b' B 'Z' > 'a' C 'A' == 'a' D '9' > 'a'

Q7

A variable of a reference type stores:

A the object itself B the address of an object C a primitive value D always null

Q8

After String t = s;, how many String objects exist?

A Two, one for each variable. B One, referred to by both variables. C None until a method is called. D It depends on the length of the string.

Q9

What happens when a method is called on a null reference?

A The call is ignored B A NullPointerException is thrown at run time C A compile-time error D The method returns null

Q10

Which statement about String objects is not true?

A A String can be created without calling a constructor. B A String literal can be reused from the string pool. C The String class is final. D String objects are mutable.

Q11

What is the output?

String s = "hello";
s.toUpperCase();
System.out.println(s);

A HELLO B hello C Hello D It does not compile.

Q12

Given String s = "Programming";, what does s.length() return?

A 10 B 11 C 12 D It does not compile.

Q13

Given String s = "Programming";, what does s.charAt(3) return?

A 'o' B 'g' C 'r' D 'a'

Q14

Given String s = "Programming";, what does s.substring(0, 3) return?

A "Pro" B "Prog" C "rog" D "Progr"

Q15

Given String s = "Programming";, what does s.substring(3) return?

A "Pro" B "gramming" C "g" D "ramming"

Q16

Given String s = "banana";, what does s.indexOf("na") return?

A 2 B 3 C 4 D −1

Q17

What does "banana".indexOf("xy") return?

A 0 B −1 C 6 D An exception is thrown.

Q18

What is the result of "Java".charAt(4)?

A 'a' B ' ' C A StringIndexOutOfBoundsException D A compile-time error

Q19

What is the output?

String a = "Java";
String b = "Java";
String c = new String("Java");
System.out.print((a == b) + " " + (a == c) + " " + a.equals(c));

A true true true B true false true C false false true D true false false

Q20

Which is the safest way to test whether name holds exactly the text "Ali"?

A name == "Ali" B "Ali".equals(name) C name.equals == "Ali" D name.compareTo("Ali")

Q21

What does "apple".compareTo("banana") return?

A A negative number B Zero C A positive number D false

Q22

What does "Hello".equalsIgnoreCase("HELLO") return?

A true B false C 0 D It does not compile.

Q23

What is the output of System.out.println(" Java ".trim().length());?

A 4 B 6 C 8 D 10

Q24

What is the output?

String s = "mississippi";
System.out.print(s.replace('s', 'z'));

A mizzizzippi B mississippi C mizsizsippi D It does not compile.

Q25

What is the output?

String s = "Wenzhou";
System.out.print(s.substring(2, 5) + s.length());

A nzh7 B nzho7 C enz7 D nzh6

Q26

Which import is required to use Scanner?

A import java.io.Scanner; B import java.util.Scanner; C import java.lang.Scanner; D No import is required.

Q27

Which statement correctly creates a Scanner that reads from the keyboard?

A Scanner in = new Scanner(); B Scanner in = new Scanner(System.in); C Scanner in = Scanner(System.in); D Scanner in = new Scanner(System.out);

Q28

Which Scanner method reads an entire line including spaces?

A next() B nextLine() C nextString() D readLine()

Q29

A program calls nextInt() and then nextLine(). What does nextLine() usually return?

A The next full line typed by the user. B An empty string, because the newline left by nextInt is consumed. C null. D It throws an exception.

Q30

Which method would you use to check that the user really typed an integer before reading it?

A isInt() B hasNextInt() C checkInt() D nextInt()

Q31

What exception is thrown by nextInt() when the user types abc?

A NumberFormatException B InputMismatchException C IOException D No exception is thrown.

Q32

What is the output when the user types Ali Hassan at the prompt?

Scanner in = new Scanner(System.in);
String word = in.next();
System.out.print(word);

A Ali Hassan B Ali C Hassan D An exception is thrown.

Q33

What is the output?

String s = "Java";
s += " SE";
s = s + 8;
System.out.print(s + " " + s.length());

A Java SE8 8 B Java SE8 9 C Java SE 8 9 D It does not compile.

Q34

Which expression converts the char variable digit (for example '7') into the int value 7?

A (int) digit B digit - '0' C digit / 10 D (int) "digit"

Q35 Short answer

Draw the memory picture produced by the three lines below and explain what each variable contains.

int n = 7;
String s = "Java";
String t = s;

Q36 Short answer

Explain what “immutable” means for String and describe what actually happens in memory when a program executes s = s + "!"; inside a loop that runs a thousand times.

Q37 Short answer

Write the three lines needed to read a student's full name and then their age from the keyboard, in that order, without falling into the nextLine trap.

Q38 Programming

Write a program Initials that reads a full name such as Hamza Djigal on one line and prints the initials in upper case separated by dots (H.D.). Use indexOf, substring and charAt; assume exactly two names.