The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
This page contains some code snippets that show you several common scenarios.
String
from a Code PointString newString(int codePoint) { return new String(Character.toChars(codePoint)); }
String
from a Code Point - Optimized for BMP CharactersThe Character.toChars
method creates an temporary array that is used once and then discarded. If this negatively affects performance, you can use the following approach that is optimized for BMP characters (characters that are represented by a single char
value). In this method, toChars
is invoked only for supplementary characters.
String newString(int codePoint) { if (Character.charCount(codePoint) == 1) { return String.valueOf(codePoint); } else { return new String(Character.toChars(codePoint)); } }
String
Objects in BulkTo create a large number of strings, the bulk version of the previous snippet reuses the array used by the toChars
method. This method creates a separate String
instance for each code point and is optimized for BMP characters.
String[] newStrings(int[] codePoints) { String[] result = new String[codePoints.length]; char[] codeUnits = new char[2]; for (int i = 0; i < codePoints.length; i++) { int count = Character.toChars(codePoints[i], codeUnits, 0); result[i] = new String(codeUnits, 0, count); } return result; }
The formatting API supports supplementary characters. The following example is a simple way to generate a message.
// recommended System.out.printf("Character %c is invalid.%n", codePoint);
This following approach is simple and avoids concatenation, which makes the text more difficult to localize as not all languages insert numeric values into a string in the same order as English.
// not recommended System.out.println("Character " + String.valueOf(char) + " is invalid.");