Java Summary - Building Java Programs: A Back to Basics Approach - page 1112

Useful Methods of the Character Class

Method Description Example

Converts a character that looks
like a number into that number

Character.getNumericValue('6') returns 6 getNumericValue(ch)

Tests whether the character is
one of the digits '0' through '9'

Character.isDigit('X') returns false isDigit(ch)

Tests whether the character is in
the range 'a' to 'z' or 'A' to 'Z'

Character.isLetter('f') returns true isLetter(ch)

Tests whether the character is a
lowercase letter

Character.isLowerCase('Q') returns false isLowerCase(ch)

Tests whether the character is an
uppercase letter

Character.isUpperCase('Q') returns true isUpperCase(ch)

Converts a character into the
lowercase version of the given
letter

Character.toLowerCase('Q') returns 'q' toLowerCase(ch)

Converts a character into the
uppercase version of the given
letter

Character.toUpperCase('x') returns 'X'

toUpperCase(ch)

Useful Methods of the Collection Interface

Method Description

Adds the specified element to this collection

add(element)

Adds all elements from the given collection to this collection addAll(collection)

Removes all elements from this collection

clear()

Returns true if this collection contains the given element contains(element)

Returns true if this collection contains all elements of the given collection

containsAll(collection)

Returns true if this collection contains no elements isEmpty()

Returns an object that can be used to traverse the elements of this collection

iterator()

Removes one occurrence of the specified element, if it is contained in this collection remove(element)

Removes all elements of the given collection from this collection

removeAll(collection)

Removes all elements not found in the given collection from this collection retainAll(collection)

Returns the number of elements in this collection

size()

Returns an array containing the elements of this collection toArray()