public static Prototype intern(String descriptor) {
    if (descriptor == null) {
      throw new NullPointerException("descriptor == null");
    }

    Prototype result = internTable.get(descriptor);
    if (result != null) {
      return result;
    }

    result = fromDescriptor(descriptor);
    return putIntern(result);
  }
Returns the unique instance corresponding to the given method descriptor. See vmspec-2 sec4.3.3
for details on the field descriptor syntax.

@param descriptor {@code non-null;} the descriptor
@return {@code non-null;} the corresponding instance
@throws IllegalArgumentException thrown if the descriptor has invalid syntax
android/android_framework/dex-maker/src/main/java/com/android/dx/rop/type/Prototype.java