The Java Developers Almanac 1.4


Order this book from Amazon.

   
Home > List of Packages > java.lang  [58 examples] > Strings  [12 examples]

e81. Determining If a String Is a Legal Java Identifier

Briefly, a valid Java identifier must start with a Unicode letter, underscore, or dollar sign ($). The other characters, if any, can be a Unicode letter, underscore, dollar sign, or digit.

For more details, see http://java.sun.com/docs/books/jls/second_edition/html/lexical.doc.html.

    // Returns true if s is a legal Java identifier.
    public static boolean isJavaIdentifier(String s) {
        if (s.length() == 0 || !Character.isJavaIdentifierStart(s.charAt(0))) {
            return false;
        }
        for (int i=1; i<s.length(); i++) {
            if (!Character.isJavaIdentifierPart(s.charAt(i))) {
                return false;
            }
        }
        return true;
    }
    // Some examples
    boolean b = isJavaIdentifier("my_var"); // true
    b = isJavaIdentifier("my_var.1");       // false
    b = isJavaIdentifier("$my_var");        // true
    b = isJavaIdentifier("\u0391var");      // true
    b = isJavaIdentifier("_");              // true
    b = isJavaIdentifier("$");              // true
    b = isJavaIdentifier("1$my_var");       // false

 Related Examples
e70. Constructing a String
e71. Comparing Strings
e72. Determining If a String Contains a Substring
e73. Getting a Substring from a String
e74. Searching a String for a Character or a Substring
e75. Replacing Characters in a String
e76. Replacing Substrings in a String
e77. Converting a String to Upper or Lower Case
e78. Converting a Primitive Type Value to a String
e79. Converting Between Unicode and UTF-8
e80. Determining a Character's Unicode Block

See also: Arrays    Assertions    Classes    Commands    Numbers    Objects    System Properties    Threads   


© 2002 Addison-Wesley.