Java requires all classes that are loaded to be verified, in order to maintain the security of the sandbox and ensure that the code is safe to optimize. Note that this is done on the bytecode level, so the verification does not verify invariants of the Java language, it merely verifies that the bytecode makes … Read more
Your code ignores the benefits of Java 5 almost completely. When you update it, you’ll get for(MethodNode mn: cn.methods) { if(!mn.name.equals(“main”)) continue; Analyzer<BasicValue> analyzer = new Analyzer<>(new BasicInterpreter()); analyzer.analyze(cn.name, mn); int i = -1; for (Frame<BasicValue> frame: analyzer.getFrames()) { i++; if(frame == null) continue; int opcode = mn.instructions.get(i).getOpcode(); if(opcode != Opcodes.ILOAD) continue; BasicValue stackValue = frame.getStack(0); … Read more
I’m not an expert, but here is my understanding: Traits are compiled into an interface and corresponding class. trait Foo { def bar = { println(“bar!”) } } becomes the equivalent of… public interface Foo { public void bar(); } public class Foo$class { public static void bar(Foo self) { println(“bar!”); } } Which leaves … Read more
Yes, calling getClass() has become a canonical “test for null” idiom, as getClass() is expected to be a cheap intrinsic operation and, I suppose, HotSpot might be capable of detecting this pattern and reduce the operation to an intrinsic null-check operation, if the result of getClass() is not used. Another example is creating an inner … Read more
Item 93 of Java Puzzlers (Joshua Bloch) says that you can work round this by preventing the final value from being considered a constant. For example: public class A { public static final int INT_VALUE = Integer.valueOf(1000).intValue(); public static final String STRING_VALUE = “foo”.toString(); } Of course none of this is relevant if you don’t … Read more
You can discover the classes using ASM‘s Remapper class (believe it or not). This class is actually meant to replace all occurrences of a class name within bytecode. For your purposes, however, it doesn’t need to replace anything. This probably doesn’t make a whole lot of sense, so here is an example… First, you create … Read more
My guess is that the point is to copy the values into local variables once, to avoid having to fetch the field value repeatedly from the heap for each iteration of the loop in the next few lines. Of course, that begs the question as to why the same comment hasn’t been applied on the … 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
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
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