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Questions and Exercises: Operators - Java Tutorial 5.0 英文版

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Trail: Learning the Java Language
Lesson: Language Basics

Questions and Exercises: Operators

Questions

1. Consider the following code snippet.

   arrayOfInts[j] > arrayOfInts[j+1]
   

   Which operators does the code contain?
2. Consider the following code snippet.

   int i = 10;
   int n = i++%5;
   

   1. What are the values of i and n after the code is executed?
   2. What are the final values of i and n if instead of using the postfix increment operator (i++), you use the prefix version (++i))?
3. What is the value of i after the following code snippet executes?

   int i = 8;
   i >>=2;
   

4. What is the value of i after the following code snippet executes?

   int i = 17;
   i >>=1;
   

Exercises

1. Write a program that tests whether a floating-point number is zero. (Hint: Generally, you shouldn't use the equality operator, ==, with floating-point numbers since floating-point numbers by nature are difficult to match exactly. Instead, test whether the number is close to zero.)
2. Write a program that calculates the number of U.S. dollars equivalent to a given number of euros. Assume an exchange rate of 0.781162 euros per dollar. If you want to control the format of the numbers your program displays, you can use the DecimalFormat class, which is discussed in the Formatting Numbers with Custom Formats section.
3. Write a program that uses the bits in a single integer to represent the true/false data shown in the following figure.

   

   Shows the true/false data to be represented by the bits in an integer.

   Include in the program a variable named status and have the program print the meaning of status. For example, if status is 1 (only bit 0 is set), the program should print something like this.

   Ready to receive requests
   

   1. Show your code.
   2. What is the output when status is 8?
   3. What is the output when status is 7?

Check your answers.

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