It seems this behavior is caused by specifying the sourceCompatibility before apply plugin: ‘java’, which happens if you try to set the compatibility option inside allprojects. In my setup, the situation can be solved by replacing: allprojects { sourceCompatibility = 1.6 targetCompatibility = 1.6 } with: allprojects { apply plugin: ‘java’ sourceCompatibility = 1.6 targetCompatibility … Read more
Lambdas are not invoked using invokedynamic, their object representation is created using invokedynamic, the actual invocation is a regular invokevirtual or invokeinterface. For example: // creates an instance of (a subclass of) Consumer // with invokedynamic to java.lang.invoke.LambdaMetafactory something(x -> System.out.println(x)); void something(Consumer<String> consumer) { // invokeinterface consumer.accept(“hello”); } Any lambda has to become an … Read more
The difference is that lookupswitch uses a table with keys and labels tableswitch uses a table with labels only. When performing a tableswitch, the int value on top of stack is directly used as an index into the table to grab the jump destination and perform the jump immediately. The whole lookup+jump process is an … Read more
NOPs serve several purposes: They allow the debugger to place a breakpoint on a line even if it is combined with others in the generated code. It allows the loader to patch a jump with a different-sized target offset. It allows a block of code to be aligned at a particular boundary, which can be … Read more
First off let me say that I don’t think that the subtle differences between Java bytecode and MSIL is something that should bother a novice .NET developer. They both serve the same purpose of defining an abstract target machine which is a layer above the physical machine being used in the end. MSIL and Java … Read more
Its a very common question. Like most performance questions the best approach is to write the clearest and simplest code you can as this improves the maintainability of the code and helps ensure it performs reasonably well even after it is changed. (Clever/Obtuse/Needlessly Verbose code can run fast to start with but as it is … Read more
In general, for any thread safety problem you will need to protect your internal data structures with locks. This can be done with various levels of granularity. You can use fine-grained locking, where every separate structure has its own lock. You can use coarse-grained locking where one lock protects everything (the GIL approach). There are … Read more
Yes. You can use the javap command that’s included with the JDK to see the byte code of a class. For example: javap -c com.mypackage.MyClass There are several libraries and tools that help you to work with Java bytecode, for example ASM and Jasmin.
The terms are indeed a bit confusing, because they are sometimes used inconsistently. Machine code: This is the most well-defined one. It is code that uses the byte-code instructions which your processor (the physical piece of metal that does the actual work) understands and executes directly. All other code must be translated or transformed into … Read more
JIT vs. Static Compiler As already said in the previous posts, JIT can compile IL/bytecode into native code at runtime. The cost of that was mentionned, but not to its conclusion: JIT has one massive problem is that it can’t compile everything: JIT compiling takes time, so the JIT will compile only some parts of … Read more