Fundamentals of Characters and Strings
Characters are the fundamental building blocks of Java source programs. Every program is composed of a sequence of characters thatwhen grouped together meaningfullyare interpreted by the computer as a series of instructions used to accomplish a task. A program may contain character literals. A character literal is an integer value represented as a character in single quotes. For example, 'z' represents the integer value of z, and ' ' represents the integer value of newline. The value of a character literal is the integer value of the character in the Unicode character set. Appendix B presents the integer equivalents of the characters in the ASCII character set, which is a subset of Unicode (discussed in Appendix F). For detailed information on Unicode, visit www.unicode.org.
Recall from Section 2.2 that a string is a sequence of characters treated as a single unit. A string may include letters, digits and various special characters, such as +, -, *, / and $. A string is an object of class String. String literals (stored in memory as String objects) are written as a sequence of characters in double quotation marks, as in:
"John Q. Doe" |
(a name) |
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"9999 Main Street" |
(a street address) |
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"Waltham, Massachusetts" |
(a city and state) |
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"(201) 555-1212" |
(a telephone number) |
A string may be assigned to a String reference. The declaration
String color = "blue";
initializes String reference color to refer to a String object that contains the string "blue".
Performance Tip 29.1
Java treats all string literals with the same contents as a single String object that has many references to it. This conserves memory. |