How to convert an array of bytes to a String in Java

Pretty funny to convert an array of bytes to a String or vice versa. String stores his value in a byte[], so the conversion should be straightforward.

Convert byte[] to String

In String.java we have a lot of constructors that accept a byte array:

String(byte[] bytes, int offset, int length, String charsetName) throws UnsupportedEncodingException 
String(byte[] bytes, String charsetName) throws UnsupportedEncodingException 
String(byte[] bytes, java.nio.charset.Charset charset) 
String(byte[] bytes, int offset, int length) 
String(byte[] bytes) 

If the Charsetis not specified Charset.defaultCharset() is used by the constructor.

An example of a simple implementation:

// we build an array of bytes from a String 
byte[] myByteArray = "marmo.dev blog".getBytes(); 
 
// now we build a String using the array 
String myNewString = new String(myByteArray); 
 
System.out.println(myNewString) // -> marmo.dev blog 

You can specify a Charset:

// Charsets are defined in java.nio.charset.StandardCharsets 
 
String myNewString = new String(myByteArray, StandardCharsets.UTF_16) 

Convert String to byte[]

In the previous example we used public byte[] getBytes() present in String.java.

This is the recommended method, you can pass a charsetName to encode correctly the array.

String myString = "marmo.dev blog en français"; 
 
byte[] myDefaultArrayOfBytes = myString.getBytes(); // byte[27] { 109, 97, 114, 99, 111, 46, 100, 101, 118, 32, 98, 108, 111, 103, 32, 101, 110, 32, 102, 114, 97, 110, -61, -89, 97, 105, 115 } 
 
byte[] myUTF8ArrayOfBytes = myString.getBytes("ISO-8859-1") // byte[26] { 109, 97, 114, 99, 111, 46, 100, 101, 118, 32, 98, 108, 111, 103, 32, 101, 110, 32, 102, 114, 97, 110, -25, 97, 105, 115 } 
 

In our example you can see how the result differs if I use the default Charset (UTF-8) and the ISO-8859-1.