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| Figure 7 . Range of values for floating-point types. |
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float
1.4E-45 to 3.4028235E38double
4.9E-324 to 1.7976931348623157E308 |
I will discuss the operations that can be performed on floating-point types in a future module.
Computers deal only in numeric values. They don't know how to deal directly with the letters of the alphabet and punctuation characters. This gives rise to a type named char .
Purpose of the char type
The purpose of the character type is to make it possible to represent the letters of the alphabet, the punctuation characters, and the numeric characters internally in the computer. This is accomplished by assigning a numeric value to each character, much as you may have done to create secret codes when you were a child.
A single character type
Java supports a single character type named char . The char type uses a standard character representation known as Unicode to represent up to 65,535 different characters.
Why so many characters?
The reason for the large number of possible characters is to make it possible to represent the characters making up the alphabets of many different countries and many different spoken languages.
What are the numeric values representing characters?
As long as the characters that you use in your program appear on your keyboard, you usually don't have a need to know the numeric value associated with the different characters. If you are curious, however, the upper-case A is represented by the value 65 inthe Unicode character set.
Representing a character symbolically
In Java, you usually represent a character in your program by surrounding it with apostrophes as shown below:
'A'.
The Java programming tools know how to cross reference that specific character symbol against the Unicode table to obtain the corresponding numeric value. (A discussion of the use of the char type to represent characters that don't appear on your keyboard is beyond the scope of this module.)
I will discuss the operations that can be performed on the char type in a future module.
The boolean type is the simplest type supported by Java. It can have only two values:
Generally speaking, about the only operations that can be directly applied to an instance of the boolean type are to change it from true to false , and vice versa. However, the boolean type can be included in a large number of somewhat higher-level operations.
The boolean type is commonly used in some sort of a test to determine what to do next, such as that shown in Figure 8 .
| Figure 8 . Example of the use of the boolean type. |
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Perform a test that returns a value of type boolean.
if that value is true,do one thing
otherwise (meaning that value is false)do a different thing |
I will discuss the operations that can be performed on the boolean type in more detail in a future module.
Extending the language
Java is an extensible programming language. By this, I mean that there is a core component to the language that is always available. Beyond the core component, different programmers can extend the language in different ways to meet their individual needs.
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