4.8. Easy Multiple Choice QuestionsΒΆ

These problems are mostly easier than what you will see on the AP CS A exam.

    4-7-1: Given the following code segment, what is in the string referenced by s1?

    1
    2
    3
    String s1 = "xy";
    String s2 = s1;
    s1 = s1 + s2 + "z";
    
  • xyz
  • s1 will equal "xy" plus another "xy" then z at the end.
  • xyxyz
  • s1 contains the original value, plus itself, plus "z"
  • xy xy z
  • No spaces are added during concatenation.
  • xy z
  • No spaces are added during concatenation, and an additional "xy" should be included at the beginning.
  • z
  • s1 was set to "xy" initially, so the final answer will be "xyxyz"

    4-7-2: What is the value of len after the following executes?

    String s1 = "Hey, buddy!";
    int len = s1.length();
    
  • 8
  • Be sure to count spaces and punctuation in the length (the number of characters in the string).
  • 10
  • Did you forget to count a space or punctuation?
  • 11
  • The length method returns the number of characters in the string, including spaces and punctuation.

    4-7-3: What is the value of pos after the following code executes?

    String s1 = "ac ded ca";
    int pos = s1.indexOf("d");
    
  • 3
  • The method indexOf returns the first position of the passed str in the current string starting from the left (from 0).
  • 4
  • The first character is at index 0 in a string, not 1.
  • 5
  • Does the indexOf method find the first occurrence of the character, or the last?
  • -1
  • Does the string contain a d? The pos method will return the first index that the character is at in the string.

    4-7-4: What is the value of s1 after the following code executes?

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    String s1 = "Hey";
    String s2 = s1.substring(0,1);
    String s3 = s2.toLowerCase();
    
  • Hey
  • Strings are immutable, meaning they don't change. Any method that that changes a string returns a new string. So s1 never changes unless you set it to a different string.
  • he
  • The substring method returns a new string starting at the first index and ending before the second index.
  • H
  • This would be true if we asked what the value of s2 was after the code executes. What is the value of s1?
  • h
  • This would be true if we asked what the value of s3 was after the code executes. What is the value of s1?
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