Java Glossary : String

Java definitions: 0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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String

Strings are quite different from C++. They are immutable , i.e. You can't change the characters in a string. To look at individual characters, you need to use charAt() . Strings in Java are 16-bit Unicode. To edit strings, you need to use a StringBuffer object or a char[] . For manipulating 8-bit characters, you want an array of bytes -- byte[] . There are three types of empty string, null, "" and " ". Here is how to check for each flavour:

if ( s == null ) echo ( "was null" );
else if ( s .length() == 0 ) echo ( "was empty" );
else if ( s .trim().length () == 0 ) echo ( "was blank or other whitespace" );

The following form:

if ( "abc" .equals (s)) echo ( "matched" );

is preferable to:

if ( s.equals ( "abc" ) ) echo ( "matched" );

because it won't give an exception if s is null.

Strings are immutable. Therefore they can be reused indefinitely, and they can be shared for many purposes. When you assign one String variable to another, no copy is made. Even when you take a substring there is no new String created. New Strings are created when:

you concatentate.
you do reads.
you foolishly use new String(String);
you use new String(somethingElse) ; for conversion.

gotchas on String comparison ¤ String redundancy ¤ stringWidth

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