user218750 user218750 - 8 months ago 89
Scala Question

Java Tuple2 difference between using accessor method and calling the variable directly

I'm using Tuple2 in my Java code, and I was wondering if there was a difference between accessing the values via the getter or just getting the variables directly.

Tuple2<String,String> tuple = new Tuple2<>("Hello", "World");
//getting values directly
String direct = tuple._1;
//using getter
String indirect = tuple._1();


The first loads a field where the second invokes the method using getField and invokeVirtual opcodes relatively. The generated byte-code looks like

  13: getfield      #6                  // Field scala/Tuple2._1:Ljava/lang/Object;
  16: checkcast     #7                  // class java/lang/String
  19: astore_2
  20: aload_1
  21: invokevirtual #8                  // Method scala/Tuple2._1:()Ljava/lang/Object;
  24: checkcast     #7                  // class java/lang/String

And the difference is the difference between a field read and a method invocation, ie the JIT compiler is happy to inline the method and it wouldn't matter much performance wise.