The {@code String} class represents character strings. All string literals in Java programs, such as {@code "abc"}, are implemented as instances of this class. <p> Strings are constant; their values cannot be changed after they are created. String buffers support mutable strings. Because String objects are immutable they can be shared. For example: <blockquote><pre> String str = "abc"; </pre></blockquote><p> is equivalent to: <blockquote><pre> char data[] = {'a', 'b', 'c'}; String str = new String(data); </pre></blockquote><p> Here are some more examples of how strings can be used: <blockquote><pre> System.out.println("abc"); String cde = "cde"; System.out.println("abc" + cde); String c = "abc".substring(2,3); String d = cde.substring(1, 2); </pre></blockquote> <p> The class {@code String} includes methods for examining individual characters of the sequence, for comparing strings, for searching strings, for extracting substrings, and for creating a copy of a string with all characters translated to uppercase or to lowercase. Case mapping is based on the Unicode Standard version specified by the {@link java.lang.Character Character} class. <p> The Java language provides special support for the string concatenation operator ( + ), and for conversion of other objects to strings. For additional information on string concatenation and conversion, see <i>The Java™ Language Specification</i>.