The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
Use the API documentation to find the answers to the following questions:
Question: 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"?
Answer: toHexString
Question: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.
Answer: valueOf
. Here's how:
String base5String = "230"; int result = Integer.valueOf(base5String, 5);
Question: What Double method can you use to detect whether a floating-point number has the special value Not a Number (NaN
)?
Answer: isNaN
Question: What is the value of the following expression, and why?
Integer.valueOf(1).equals(Long.valueOf(1))
Answer: False. The two objects (the Integer
and the Long
) have different types.
Exercise: 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?
Answer: See
MinVariablesDemo
. Here is the output:
The smallest byte value is -128 The smallest short value is -32768 The smallest integer value is -2147483648 The smallest long value is -9223372036854775808 The smallest float value is 1.4E-45 The smallest double value is 4.9E-324
Exercise: 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
.
Answer: See
Adder
.
Exercise: Create a program that is similar to the previous one but has the following differences:
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 (.
).
Answer: See
FPAdder
.