Why is L the prefix for reference types (instead of some other letter)? [duplicate]

Question

Why was L chosen as the prefix for references in type signatures? Does L stand for something, like B stands for byte, and I stands for int? Or was it chosen because C was already assigned to char?

For example,

System.out.println( new String[0].getClass().getName() );

Yields:

[Ljava.lang.String;

I'm already aware of the explanations in the Java spec and the Class.getName method javadoc.

Answer 1

This character stem from JVM internal signature and class name representation.

See JVM Specification §4.3.2. Field Descriptors:

  B   byte       signed byte
  C   char       Unicode character code point in the Basic Multilingual Plane,
                 encoded with UTF-16
  D   double     double-precision floating-point value
  F   float      single-precision floating-point value
  I   int        integer
  J   long       long integer
  L ClassName ;  reference             an instance of class ClassName
  S   short      signed short
  Z   boolean    true or false
  [   reference  one array dimension

The array type consist of a [ for each dimension, followed by their element signature, e.g. [I for int[]. Similiarly, Object[] is represented by [Ljava/lang/Object; internally.

It seems, when the conversion from internal class name to application visible name, i.e. returned by Class.getName() was first implemented, it was implemented as just converting / to . but without care for the array notation. Later on, it wasn’t changed for compatibility reasons.

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Note the Java 8 introduced getTypeName() to solve the issue, i.e. String[].class.getTypeName() yields java.lang.String[].