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4.8. Easy Multiple Choice Questions¶
These problems are mostly easier than what you will see on the AP CS A exam.
- s1 will equal "xy" plus another "xy" then z at the end.
- 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.
- s1 was set to "xy" initially, so the final answer will be "xyxyz"
4-7-1: Given the following code segment, what is in the string referenced by s1?
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String s1 = "xy"; String s2 = s1; s1 = s1 + s2 + "z";
- Be sure to count spaces and punctuation in the length (the number of characters in the string).
- Did you forget to count a space or punctuation?
- The length method returns the number of characters in the string, including spaces and punctuation.
4-7-2: What is the value of len after the following executes?
String s1 = "Hey, buddy!"; int len = s1.length();
- The method indexOf returns the first position of the passed str in the current string starting from the left (from 0).
- The first character is at index 0 in a string, not 1.
- Does the indexOf method find the first occurrence of the character, or the last?
- Does the string contain a d? The pos method will return the first index that the character is at in the string.
4-7-3: What is the value of pos after the following code executes?
String s1 = "ac ded ca"; int pos = s1.indexOf("d");
- 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.
- The substring method returns a new string starting at the first index and ending before the second index.
- This would be true if we asked what the value of s2 was after the code executes. What is the value of s1?
- This would be true if we asked what the value of s3 was after the code executes. What is the value of s1?
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();