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Computational Problem Solving with Java and Interactive Object Graphics

Mark F. Russo, PhD

Section 2.4 Character Primitives

In Java, the char primitive type is used to represent a single character. It can hold any character from the ASCII or Unicode character sets, which includes characters from various languages and scripts.
The char type is declared using the keyword char and occupies 2 bytes of memory. It can store characters using either their Unicode representation or the corresponding escape sequences. For example:
char letterA = 'A';
char digit7 = '7';
char euroSymbol = '\u20AC'; // Unicode representation for the Euro symbol
char newLine = '\n';        // Escape sequence for a new line
In the above examples, letterA stores the character ’A’, digit7 stores the character ’7’, euroSymbol stores the Euro symbol (€), and newLine stores the newline command character.
Java provides various methods and operators to work with char values. Some commonly used methods include:
Table 2.4.1.
Character.isLetter(char ch) Checks if the specified character is a letter.
Character.isDigit(char ch) Checks if the specified character is a digit.
Character.isWhitespace(char ch) Checks if the specified character is whitespace.
Character.toLowerCase(char ch) Converts the specified character to lowercase.
Character.toUpperCase(char ch) Converts the specified character to uppercase.
Note that char values can also be used in arithmetic expressions, as they are internally represented as two-byte integers, similar to a short. For example, in JShell:
jshell> char ch;                // Declare a char variable ch
ch ==> '\000'                   // Default value of 0
|  created variable ch : char

jshell> ch = 'A' + 1;           // Assign 'A' + 1 to it
ch ==> 'B'
|  assigned to ch : char

jshell> ch                      // The value of ch is 'B'
ch ==> 'B'                      // ASCII code for 'A' is 65 and 'B' is 66
|  value of ch : char

jshell>
Overall, the char primitive type in Java allows you to work with individual characters, making it useful for text processing, string manipulation, and various other tasks involving character-level operations.

Activity 2.4.1.

Using JShell in verbose mode, enter a char literal using single-quote notation. Make sure that JShell tells you that your literal is of type char.
Answer.
jshell> 'A'
$1 ==> 'A'
|  created scratch variable $1 : char

Activity 2.4.2.

What happens if you enter a multi-char char literal, like 'abc'? Why do you get that response?
Answer.
JShell prints the error unclosed character literal, because it was expecting another ' but found a different character instead.

Activity 2.4.3.

chars are stored as two-byte numbers. To what does the expression 'A' + 0; evaluate?
Answer.
65

Activity 2.4.4.

What does the previous result tell you about the way capital-A is stored in memory?
Hint.
What is ASCII code for capital-A? (Refer to ASCII Table).
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