Is Hadoop Text datatype mutable or immutable?

Question

In one of the mapreduce program, I was using new Text() during context.write.

context.write(key, new Text(outputRecord.toDelimitedString("|")));

As I am using above statement, I want to know how Text objects are stored and how memory management is being handled. Also want to know about existence of a object value after not referred by any object.

Please let me know about this.

Answer 1

No Text in Hadoop is not immutable. It can't be, because Hadoop's serialization process implicitly forbids immutability.

In this particular case, context.write will just serialize the content of Text into a byte buffer directly inside the call, so the Text object will be trashed soon after the method returns.

Keep in mind that there is still a stack reference to the Text object as it is passed into the method, so it won't be eligible for garbage collection.