Strings - Liang
The following program displays __________. public class Test { public static void main(String[] args) { String s = "Java"; StringBuilder buffer = new StringBuilder(s); change(s); System.out.println(s); } private static void change(String s) { s = s + " and HTML"; } } A. Java B. Java and HTML C. and HTML D. nothing is displayed
A. Java The correct answer is A Explanation: Inside the method, the statement s = s + ' and HTML' creates a new String object s, which is different from the original String object passed to the change(s) method. The original String object has not been changed. Therefore, the output from the original string is Java.
Which of the following statements is preferred to create a string "Welcome to Java"? A. String s = "Welcome to Java"; B. String s = new String("Welcome to Java"); C. String s; s = "Welcome to Java"; D. String s; s = new String("Welcome to Java");
A. String s = "Welcome to Java";
Suppose s1 and s2 are two strings. Which of the following statements or expressions is incorrect? A. String s3 = s1 - s2; B. boolean b = s1.compareTo(s2); C. char c = s1[0]; D. char c = s1.charAt(s1.length());
A. String s3 = s1 - s2; B. boolean b = s1.compareTo(s2); C. char c = s1[0]; D. char c = s1.charAt(s1.length());
__________ returns a string. A. String.valueOf(123) B. String.valueOf(12.53) C. String.valueOf(false) D. String.valueOf(new char[]{'a', 'b', 'c'})
A. String.valueOf(123) B. String.valueOf(12.53) C. String.valueOf(false) D. String.valueOf(new char[]{'a', 'b', 'c'})
Analyze the following code. class Test { public static void main(String[] args) { String s; System.out.println("s is " + s); } } A. The program has a compilation error because s is not initialized, but it is referenced in the println statement. B. The program has a runtime error because s is not initialized, but it is referenced in the println statement. C. The program has a runtime error because s is null in the println statement. D. The program compiles and runs fine.
A. The program has a compilation error because s is not initialized, but it is referenced in the println statement.
Which of the following is true? A. You can add characters into a string buffer. B. You can delete characters into a string buffer. C. You can reverse the characters in a string buffer. D. The capacity of a string buffer can be automatically adjusted.
A. You can add characters into a string buffer. B. You can delete characters into a string buffer. C. You can reverse the characters in a string buffer. D. The capacity of a string buffer can be automatically adjusted.
What is the return value of "SELECT".substring(4, 4)? A. an empty string B. C C. T D. E
A. an empty string
The StringBuilder methods _____________ not only change the contents of a string buffer, but also returns a reference to the string buffer. A. delete B. append C. insert D. reverse E. replace
A. delete B. append C. insert D. reverse E. replace
To check if a string s contains the suffix "Java", you may write A. if (s.endsWith("Java")) ... B. if (s.lastIndexOf("Java") >= 0) ... C. if (s.substring(s.length() - 4).equals("Java")) ... D. if (s.substring(s.length() - 5).equals("Java")) ... E. if (s.charAt(s.length() - 4) == 'J' && s.charAt(s.length() - 3) == 'a' && s.charAt(s.length() - 2) == 'v' && s.charAt(s.length() - 1) == 'a') ...
A. if (s.endsWith("Java")) ... C. if (s.substring(s.length() - 4).equals("Java")) ... E. if (s.charAt(s.length() - 4) == 'J' && s.charAt(s.length() - 3) == 'a' && s.charAt(s.length() - 2) == 'v' && s.charAt(s.length() - 1) == 'a') ...
To check if a string s contains the prefix "Java", you may write A. if (s.startsWith("Java")) ... B. if (s.indexOf("Java") == 0) ... C. if (s.substring(0, 4).equals("Java")) ... D. if (s.charAt(0) == 'J' && s.charAt(1) == 'a' && s.charAt(2) == 'v' && s.charAt(3) == 'a') ...
A. if (s.startsWith("Java")) ... B. if (s.indexOf("Java") == 0) ... C. if (s.substring(0, 4).equals("Java")) ... D. if (s.charAt(0) == 'J' && s.charAt(1) == 'a' && s.charAt(2) == 'v' && s.charAt(3) == 'a') ...
Which code fragment would correctly identify the number of arguments passed via the command line to a Java application, excluding the name of the class that is being invoked? A. int count = args.length; B. int count = args.length - 1; C. int count = 0; while (args[count] != null) count ++; D. int count=0; while (!(args[count].equals(""))) count ++;
A. int count = args.length;
Which of the following is the correct header of the main method? A. public static void main(String[] args) B. public static void main(String args[]) C. public static void main(String[] x) D. public static void main(String x[]) E. static void main(String[] args)
A. public static void main(String[] args) B. public static void main(String args[]) C. public static void main(String[] x) D. public static void main(String x[]) The correct answer is ABCD Explanation: e is incorrect because the main method must be public.
What is the output of the following code? public class Test { public static void main(String[] args) { String s1 = new String("Welcome to Java!"); String s2 = new String("Welcome to Java!"); if (s1.equals(s2)) System.out.println("s1 and s2 have the same contents"); else System.out.println("s1 and s2 have different contents"); } } A. s1 and s2 have the same contents B. s1 and s2 have different contents
A. s1 and s2 have the same contents
What is the output of the following code? public class Test { public static void main(String[] args) { String s1 = "Welcome to Java!"; String s2 = "Welcome to Java!"; if (s1 == s2) System.out.println("s1 and s2 reference to the same String object"); else System.out.println("s1 and s2 reference to different String objects"); } } A. s1 and s2 reference to the same String object B. s1 and s2 reference to different String objects
A. s1 and s2 reference to the same String object
What is the output of the following code? public class Test { public static void main(String[] args) { String s1 = "Welcome to Java!"; String s2 = s1; if (s1 == s2) System.out.println("s1 and s2 reference to the same String object"); else System.out.println("s1 and s2 reference to different String objects"); } } A. s1 and s2 reference to the same String object B. s1 and s2 reference to different String objects
A. s1 and s2 reference to the same String object
_________ returns the last character in a StringBuilder variable named strBuf? A. strBuf.charAt(strBuf.length() - 1) B. strBuf.charAt(strBuf.capacity() - 1) C. StringBuilder.charAt(strBuf.length() - 1) D. StringBuilder.charAt(strBuf.capacity() - 1)
A. strBuf.charAt(strBuf.length() - 1)
Suppose s1 and s2 are two strings. What is the result of the following code? s1.equals(s2) == s2.equals(s1) A. true B. false
A. true
Suppose Character x = new Character('a'), __________________ returns true. A. x.equals(new Character('a')) B. x.compareToIgnoreCase('A') C. x.equalsIgnoreCase('A') D. x.equals('a') E. x.equals("a")
A. x.equals(new Character('a')) D. x.equals('a') Explanation: (B) and (C) are wrong because no methods compareToIgnoreCase and equalsIgnoreCase are in the Character class. (E) is wrong because a character is not a string.
What is the return value of "SELECT".substring(0, 5)? A. "SELECT" B. "SELEC" C. "SELE" D. "ELECT"
B. "SELEC"
"abc".compareTo("aba") returns ___________. A. 1 B. 2 C. -1 D. -2 E. 0
B. 2
What is displayed by the following code? String[] tokens = "A,B;C;D".split("[,;]"); for (int i = 0; i < tokens.length; i++) System.out.print(tokens[i] + " "); A. A,B;C;D B. A B C D C. A B C;D D. A B;C;D
B. A B C D
The following program displays __________. public class Test { public static void main(String[] args) { String s = "Java"; StringBuilder buffer = new StringBuilder(s); change(buffer); System.out.println(buffer); } private static void change(StringBuilder buffer) { buffer.append(" and HTML"); } } A. Java B. Java and HTML C. and HTML D. nothing is displayed
B. Java and HTML The correct answer is B Explanation: Inside the method, the content of the StringBuilder object is changed to Java and HTML. Therefore, the output from buffer is Java and HTML.
Which correctly creates an array of five empty Strings? A. String[] a = new String [5]; B. String[] a = {"", "", "", "", ""}; C. String[5] a; D. String[ ] a = new String [5]; for (int i = 0; i < 5; a[i++] = null);
B. String[] a = {"", "", "", "", ""};
Which of the following is the correct statement to return a string from an array a of characters? A. toString(a) B. new String(a) C. convertToString(a) D. String.toString(a)
B. new String(a)
Assume s is "ABCABC", the method __________ returns an array of characters. A. toChars(s) B. s.toCharArray() C. String.toChars() D. String.toCharArray() E. s.toChars()
B. s.toCharArray()
What is the output of the following code? public class Test { public static void main(String[] args) { String s1 = new String("Welcome to Java!"); String s2 = new String("Welcome to Java!"); if (s1 == s2) System.out.println("s1 and s2 reference to the same String object"); else System.out.println("s1 and s2 reference to different String objects"); } } A. s1 and s2 reference to the same String object B. s1 and s2 reference to different String objects
B. s1 and s2 reference to different String objects
What is the output of the following code? public class Test { public static void main(String[] args) { String s1 = new String("Welcome to Java"); String s2 = s1; s1 += "and Welcome to HTML"; if (s1 == s2) System.out.println("s1 and s2 reference to the same String object"); else System.out.println("s1 and s2 reference to different String objects"); } } A. s1 and s2 reference to the same String object B. s1 and s2 reference to different String objects
B. s1 and s2 reference to different String objects
Which of the following is the correct statement to return JAVA? A. toUpperCase("Java") B. "Java".toUpperCase("Java") C. "Java".toUpperCase() D. String.toUpperCase("Java")
C. "Java".toUpperCase()
____________________ returns true. A. "peter".compareToIgnoreCase("Peter") B. "peter".compareToIgnoreCase("peter") C. "peter".equalsIgnoreCase("Peter") D. "peter".equalsIgnoreCase("peter") E. "peter".equals("peter")
C. "peter".equalsIgnoreCase("Peter") D. "peter".equalsIgnoreCase("peter") E. "peter".equals("peter")
Given the following program: public class Test { public static void main(String[] args) { for (int i = 0; i < args.length; i++) { System.out.print(args[i] + " "); } } } What is the output, if you run the program using java Test 1 2 3 A. 3 B. 1 C. 1 2 3 D. 1 2
C. 1 2 3
What is displayed by the following code? System.out.print("A,B;C".replaceAll(",;", "#") + " "); System.out.println("A,B;C".replaceAll("[,;]", "#")); A. A B C A#B#C B. A#B#C A#B#C C. A,B;C A#B#C D. A B C A B C
C. A,B;C A#B#C
What is displayed by the following statement? System.out.println("Java is neat".replaceAll("is", "AAA")); A. JavaAAAneat B. JavaAAA neat C. Java AAA neat D. Java AAAneat
C. Java AAA neat
Suppose s is a string with the value "java". What will be assigned to x if you execute the following code? char x = s.charAt(4); A. 'a' B. 'v' C. Nothing will be assigned to x, because the execution causes the runtime error StringIndexOutofBoundsException.
C. Nothing will be assigned to x, because the execution causes the runtime error StringIndexOutofBoundsException.
Assume StringBuilder strBuf is "ABCCEFC", after invoking _________, strBuf contains "ABTTEFT". A. strBuf.replace('C', 'T') B. strBuf.replace("C", "T") C. strBuf.replace("CC", "TT") D. strBuf.replace('C', "TT") E. strBuf.replace(2, 7, "TTEFT")
E. strBuf.replace(2, 7, "TTEFT")
Analyze the following code. class Test { public static void main(String[] args) { StringBuilder strBuf = new StringBuilder(4); strBuf.append("ABCDE"); System.out.println("What's strBuf.charAt(5)? " + strBuf.charAt(5)); } } A. The program has a compilation error because you cannot specify initial capacity in the StringBuilder constructor. B. The program has a runtime error because because the buffer's capacity is 4, but five characters "ABCDE" are appended into the buffer. C. The program has a runtime error because the length of the string in the buffer is 5 after "ABCDE" is appended into the buffer. Therefore, strBuf.charAt(5) is out of range. D. The program compiles and runs fine.
C. The program has a runtime error because the length of the string in the buffer is 5 after "ABCDE" is appended into the buffer. Therefore, strBuf.charAt(5) is out of range. Explanation: The charAt method returns the character at a specific index in the string buffer. The first character of a string buffer is at index 0, the next at index 1, and so on. The index argument must be greater than or equal to 0, and less than the length of the string buffer.
What is displayed by the following code? public static void main(String[] args) { String[] tokens = "Welcome to Java".split("o"); for (int i = 0; i < tokens.length; i++) { System.out.print(tokens[i] + " "); } } A. Welcome to Java B. Welc me to Java C. Welc me t Java D. Welcome t Java
C. Welc me t Java
How can you get the word "abc" in the main method from the following call? java Test "+" 3 "abc" 2 A. args[0] B. args[1] C. args[2] D. args[3]
C. args[2]
Which of following is not a correct method in Character? A. isLetterOrDigit(char) B. isLetter(char) C. isDigit() D. toLowerCase(char) E. toUpperCase()
C. isDigit() E. toUpperCase()
Assume s is "ABCABC", the method __________ returns a new string "aBCaBC". A. s.toLowerCase(s) B. s.toLowerCase() C. s.replace('A', 'a') D. s.replace('a', 'A') E. s.replace("ABCABC", "aBCaBC")
C. s.replace('A', 'a') E. s.replace("ABCABC", "aBCaBC")
Suppose s1 and s2 are two strings. Which of the following statements or expressions are incorrect? A. String s = new String("new string"); B. String s3 = s1 + s2 C. s1 >= s2 D. int i = s1.length E. s1.charAt(0) = '5'
C. s1 >= s2 D. int i = s1.length E. s1.charAt(0) = '5'
What is the output of the following code? public class Test { public static void main(String[] args) { String s1 = new String("Welcome to Java!"); String s2 = s1.toUpperCase(); if (s1 == s2) System.out.println("s1 and s2 reference to the same String object"); else if (s1.equals(s2)) System.out.println("s1 and s2 have the same contents"); else System.out.println("s1 and s2 have different contents"); } } A. s1 and s2 reference to the same String object B. s1 and s2 have the same contents C. s1 and s2 have different contents
C. s1 and s2 have different contents
Assume StringBuilder strBuf is "ABCDEFG", after invoking _________, strBuf contains "AEFG". A. strBuf.delete(0, 3) B. strBuf.delete(1, 3) C. strBuf.delete(1, 4) D. strBuf.delete(2, 4)
C. strBuf.delete(1, 4)
Assume StringBuilder strBuf is "ABCDEFG", after invoking _________, strBuf contains "ABCRRRRDEFG". A. strBuf.insert(1, "RRRR") B. strBuf.insert(2, "RRRR") C. strBuf.insert(3, "RRRR") D. strBuf.insert(4, "RRRR")
C. strBuf.insert(3, "RRRR")
"AbA".compareToIgnoreCase("abC") returns ___________. A. 1 B. 2 C. -1 D. -2 E. 0
D. -2
Identify the problems in the following code. public class Test { public static void main(String argv[]) { System.out.println("argv.length is " + argv.length); } } A. The program has a compile error because String argv[] is wrong and it should be replaced by String[] args. B. The program has a compile error because String args[] is wrong and it should be replaced by String args[]. C. If you run this program without passing any arguments, the program would have a runtime error because argv is null. D. If you run this program without passing any arguments, the program would display argv.length is 0.
D. If you run this program without passing any arguments, the program would display argv.length is 0.
What is the output of the following code? String s = "University"; s.replace("i", "ABC"); System.out.println(s); A. UnABCversity B. UnABCversABCty C. UniversABCty D. University
D. University
What is displayed by the following code? System.out.print("Hi, ABC, good".matches("ABC ") + " "); System.out.println("Hi, ABC, good".matches(".*ABC.*")); A. false fasle B. true fasle C. true true D. false true
D. false true
Assume s is " abc ", the method __________ returns a new string "abc". A. s.trim(s) B. trim(s) C. String.trim(s) D. s.trim()
D. s.trim()
