Java strings
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The document discusses the Java String class and its API. It notes that String represents character strings rather than character arrays. Strings are immutable and methods that appear to modify the string actually return new strings while leaving the original unchanged. Important instance methods for transforming and extracting data from strings are listed, along with regular expressions and chaining methods. Static methods like valueOf are also mentioned.
Java strings
- 2. String • Class provided by the JDK. • Represents character strings, not same as an array of characters. • Any string literal such as “abc” represents an instance of the String class. • Strings are constant (immutable), CANNOT be modified after creation.
- 3. String API transformations • Many methods in the String API to transform the string. • Gives the impression that Strings can be modified. • However, all the methods return a new String, the original string is unchanged. • String API methods can be chained.
- 4. Important Instance Methods from the String API • charAt, compareTo, concat ( + operator), contains • format • getChars • indexOf, isEmpty • lastIndexOf, Length • matches • replace, replaceAll, replaceFirst, • split, startsWith, substring • toCharArray, toLowerCase, toUpperCase, trim
- 5. Regular Expressions • Used by the matches method of the String class. • Java Regular Expressions Tutorial
- 6. Chaining methods • String orig = “ Hello, how are you? “; • String modified = orig.trim().toUpperCase().substring(3,8); • Each of the above methods returns a new instance of a String. • The original String (orig) remains unchanged.
- 7. Static Methods of String API • valueOf returns the string representation of different primitive types, char array or any Object.