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 anint
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 equivalentint
? 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 variablesaChar
andaBoolean
. 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 onValueOfDemo
. -
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 (.
).