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String constructor methods.
Conversely, you can convert a String object into a byte
array of non-Unicode characters with the String.getBytes
method. When invoking either of these methods, you specify the encoding
identifier as one of the parameters.
The example that follows converts characters between UTF-8 and Unicode.
UTF-8 is a transmission format for Unicode that is safe for UNIX file
systems. The full source code for the example is in the file
StringConverter.java.
The StringConverter
program starts by creating a String
containing Unicode characters:
String original = new String("A" + "\u00ea" + "\u00f1" +
"\u00fc" + "C");
When printed, the String named original
appears as:
AêñüC
To convert the String
object to UTF-8, invoke the getBytes
method and specify the appropriate encoding identifier as a parameter.
The getBytes
method returns an array of bytes in UTF-8 format. To create a String
object from an array of non-Unicode bytes, invoke the String
constructor with the encoding parameter.
The code that makes these calls is enclosed in a try block,
in case the specified encoding is unsupported:
try {
byte[] utf8Bytes = original.getBytes("UTF8");
byte[] defaultBytes = original.getBytes();
String roundTrip = new String(utf8Bytes, "UTF8");
System.out.println("roundTrip = " + roundTrip);
System.out.println();
printBytes(utf8Bytes, "utf8Bytes");
System.out.println();
printBytes(defaultBytes, "defaultBytes");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
The StringConverter
program prints out the values in the utf8Bytes
and defaultBytes
arrays to demonstrate an important point: The length of the converted
text might not be the same as the length of the source text. Some
Unicode characters translate into single bytes, others into pairs or
triplets of bytes.
The printBytes method displays the byte arrays by invoking
the byteToHex method, which is defined in the source file,
UnicodeFormatter.java.
Here is the printBytes method:
public static void printBytes(byte[] array, String name) {
for (int k = 0; k < array.length; k++) {
System.out.println(name + "[" + k + "] = " + "0x" +
UnicodeFormatter.byteToHex(array[k]));
}
}
The output of the printBytes
method follows. Note that only the first and last bytes, the A and C
characters, are the same in both arrays:
utf8Bytes[0] = 0x41 utf8Bytes[1] = 0xc3 utf8Bytes[2] = 0xaa utf8Bytes[3] = 0xc3 utf8Bytes[4] = 0xb1 utf8Bytes[5] = 0xc3 utf8Bytes[6] = 0xbc utf8Bytes[7] = 0x43 defaultBytes[0] = 0x41 defaultBytes[1] = 0xea defaultBytes[2] = 0xf1 defaultBytes[3] = 0xfc defaultBytes[4] = 0x43
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