Questions and Exercises: Numbers

Questions

  • Use the API documentation to find the answers to the following questions:

  • What Integer method can you use to convert an int into a string that expresses the number in hexadecimal? For example, what method converts the integer 65 into the string "41"?

    • What Integer method would you use to convert a string expressed in base 5 into the equivalent int ? For example, how would you convert the string "230" into the integer value 65? Show the code you would use to accomplish this task.

    • What Double method can you use to detect whether a floating-point number has the special value Not a Number ( NaN )?

  • What is the value of the following expression, and why?

Integer.valueOf(1).equals(Long.valueOf(1))

Exercises

  • Change MaxVariablesDemo to show minimum values instead of maximum values. You can delete all code related to the variables aChar and aBoolean . What is the output?

  • Create a program that reads an unspecified number of integer arguments from the command line and adds them together. For example, suppose that you enter the following:

java Adder 1 3 2 10

The program should display 16 and then exit. The program should display an error message if the user enters only one argument. You can base your program on ValueOfDemo.

  • Create a program that is similar to the previous one but has the following differences:

  • Instead of reading integer arguments, it reads floating-point arguments.

  • It displays the sum of the arguments, using exactly two digits to the right of the decimal point.

For example, suppose that you enter the following:

java FPAdder 1 1e2 3.0 4.754

The program would display 108.75 . Depending on your locale, the decimal point might be a comma ( , ) instead of a period ( . ).

Check your answers.