Is Java UTF-8 Charset exception possible?

Question

使用"UTF-8"编码时，Java 是否可能抛出UnsupportedEncodingException ，或者我可以安全地抑制它的抛出？

Answer 1

As McDowell noted in a comment to templatetypdef's answer : If you use a Charset object when you instantiate a new String instead of passing the name of the charset, you don't have to deal with an UnsupportedEncodingException or any other checked exception:

byte[] bytes = ...;

// Requires you to handle UnsupportedEncodingException
String s1 = new String(bytes, "UTF-8");

// Doesn't require you to handle any checked exceptions
String s2 = new String(bytes, Charset.forName("UTF-8"));

It's an inconsistency in Java's standard library that we have to live with...

Note that Charset.forName(...) can throw exceptions ( IllegalCharsetNameException , IllegalArgumentException , UnsupportedCharsetException ), but these are all unchecked exceptions, so you don't have to catch or re-throw them yourself.

edit - Since Java 7 there's class java.nio.charset.StandardCharsets which has constants for frequently used character encodings. Example:

String s3 = new String(bytes, StandardCharsets.UTF_8);

Answer 2

According to the Javadoc for Charset , every Java implementation must support UTF-8, along with a few other charsets. Therefore, I think you can safely suppress the exception; unless you have a non-compliant Java implementation, this shouldn't be able to fail.

Answer 3

The most simple way is to create a UTF-8 charset constant. Then you don't have to catch the UnsupportedEncodingException again and again:

public class Charsets {
    public static final Charset UTF_8 = Charset.forName("UTF-8");
}

Edit (2014-04):

With Java 7 you don't have to create your own constant. You can simply use StandardCharsets.UTF_8 instead.

Answer 4

It's supposed to be present in every Java runtime, so it is reasonable to re-throw a runtime exception if it is missing. I wouldn't call that "suppressing," though. To me, suppressing means catching the exception and pretending it didn't happen; not sure how you'd proceed if the encoding is missing.

Answer 5

It depends what you mean by "safe" and "suppress".

I'd be tempted to catch the exception and throw an unchecked exception (or AssertionError ) in its place. The chances are that your application will never experience this. But who knows ... someone might run it on some non-conformant platform in which UTF-8 was not available. And it costs almost nothing to do this ... especially since you have to "do something" with the original exception.

Answer 6

i Have used the below line of code and it worked for me

Old code

byte[] hash = digest.digest(input.getBytes("UFT-8"));

Updated Code

byte[] hash = digest.digest(input.getBytes(StandardCharsets.UTF_8));