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Questions and Exercises: Characters and Strings - Java Tutorial 5.0 英文版

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Trail: Learning the Java Language
Lesson: Object Basics and Simple Data Objects

Questions and Exercises: Characters and Strings

Questions

1. What is the initial capacity of the following string buffer?

   StringBuffer sb = new StringBuffer("Able was I ere I saw Elba.");
   

   
   
2. Consider the following string:

   String hannah = "Did Hannah see bees? Hannah did.";
   

   1. What is the value displayed by the expression hannah.length()?
   2. What is the value returned by the method call hannah.charAt(12)?
   3. Write an expression that refers to the letter b in the string referred to by hannah.
      
      
3. How long is the string returned by the following expression? What is the string?

   "Was it a car or a cat I saw?".substring(9, 12)
   

   
   
4. In the following program, called ComputeResult, what is the value of result after each numbered line executes?

   public class ComputeResult {
       public static void main(String[] args) {
           String original = "software";
           StringBuffer result = new StringBuffer("hi");
           int index = original.indexOf('a');
   
   /*1*/   result.setCharAt(0, original.charAt(0));
   /*2*/   result.setCharAt(1, original.charAt(original.length()-1));
   /*3*/   result.insert(1, original.charAt(4));
   /*4*/   result.append(original.substring(1,4));
   /*5*/   result.insert(3, (original.substring(index, index+2) + " "));
   
           System.out.println(result);
       }
   }
   

Exercises

1. Show two ways to concatenate the following two strings together to get the string "Hi, mom.":

   String hi = "Hi, ";
   String mom = "mom.";
   

2. Write a program that computes your initials from your full name and displays them.
   
3. An anagram is a word or a phrase made by transposing the letters of another word or phrase; for example, "parliament" is an anagram of "partial men," and "software" is an anagram of "swear oft." Write a program that figures out whether one string is an anagram of another string. The program should ignore white space and punctuation.

Check your answers.

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