String Buffer: Difference between revisions

Revision as of 10:52, 24 January 2010

Revision as of 09:52, 22 March 2010

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[[Java (Sun)|Java]]'s standard way to handle text is to use its <code>{{Javadoc:SE|java/lang|String}}</code> [[Class (computer science)|class]]. Any given <code>String</code> in Java is an [[immutable object]], which means its [[State (computer science)|state]] cannot be changed. A <code>String</code> has an [[Array data type|array]] of [[Character (computing)|characters]]. Whenever a <code>String</code> must be manipulated, any changes require the creation of a new <code>String</code> (which, turn, involves the creation of a new array of characters, and copying of the original array). This happens even if the original <code>String</code>'s value or intermediate <code>String</code>s used for the manipulation are not kept.

Java provides an alternate class for string manipulation, called a <code>'''[http://java.sun.com/j2se/1.5.0/docs/api/java/lang/StringBuffer.html StringBuffer]'''</code> (see also <code>[[StringBuffer and StringBuilder]]</code>). A <code>StringBuffer</code>, like a <code>String</code>, has an array to hold characters. It, however, is mutable (its state can be altered). Its array of characters is not necessarily completely filled (as oppose to a String, whose array is always the exact required length for its contents). Thus, it has the capability to add, remove, or change its state without creating a new object (and without the creation of a new array, and array copying). The exception to this is when its array is no longer of suitable length to hold its content. In this case, it is required to create a new array, and copy contents.

For these reasons, Java would handle an expression like