CharsetDecoder detectedCharset() method in Java with Examples

The detectedCharset() method is a built-in method of the java.nio.charset.CharsetDecoder class, which retrieves the charset that this decoder has detected. The default implementation of this method always throws an UnsupportedOperationException. It should be overridden by auto-detecting decoders to return true once the input charset has been determined.

This method returns the specific Charset detected during the decoding process, allowing developers to understand which encoding was applied. If the decoder does not support auto-detection, this method will typically return the default or predefined charset associated with the decoder. It is particularly helpful in applications dealing with diverse or unpredictable input encodings.

Syntax:

Parameters: There are no parameters accepted by the above method.

Return Value: The charset that this decoder has identified is returned by the function.

Exception: If this decoder does not implement an auto-detecting charset, it throws an UnsupportedOperationException; if not enough bytes have been read to determine a charset, it throws an IllegalStateException.

Example 1:

The program's use of the CharsetDecoder and its detectedCharset() method is demonstrated by the below code. In order to create a CharsetDecoder for the "ISO-2022-CN" encoding, the program first creates a Charset instance and then uses the newDecoder() method. To find out which particular charset was found during decoding, the code tries to call the detectedCharset() function. Additionally, there is likely to be an exception when using detectedCharset() since "ISO-2022-CN" is not an auto-detecting charset; this is caught and displayed. The functionality of the detectedCharset() method using non-auto-detecting charsets is clearly shown by the code.

Implementation:

FileName: DetectedCharsetExample1.java

Output:

 The CharsetDecoder is given by: sun.nio.cs.ext.ISO2022_CN$Decoder@330bedb4 java.lang.UnsupportedOperationException 

Example 2:

The CharsetDecoder class is used in this code to operate with the "x-windows-949" character encoding. Initially it creates a Charset instance for this encoding, and then it uses the newDecoder() function to create a CharsetDecoder object. The specifics of the CharsetDecoder are displayed through printing. In order to identify the detected character set during decoding, the code then tries to invoke the detectedCharset() method. However, using this technique causes an error, which is handled and displayed because "x-windows-949" is not an auto-detecting charset. When dealing with non-auto-detecting charsets, this demonstrates the detectedCharset() method's limits.

Implementation:

FileName: DetectedCharsetExample2.java

Output:

 The CharsetDecoder is given by: sun.nio.cs.DoubleByte$Decoder@135fbaa4 java.lang.UnsupportedOperationException