Approaches to stack extraction.

StackWalkerExtraction.java

import org.openjdk.jmh.annotations.Benchmark;

public class StackWalkerExtraction {

    private static Object call(int depth, Callable<?> result) throws Exception {
        if (depth == 0) {
            return result.call();
        } else {
            return call(depth - 1, result);
        }
    }

    @Benchmark
    public Object snapshot() throws Exception {
        return call(100, () -> StackWalker.getInstance().walk(new InstanaWalker(35, 0)));
    }

    @Benchmark
    public Object complete() throws Exception {
        return call(100, () -> StackWalker.getInstance().walk(new InstanaWalker(35, 0)));
    }

    private class RawWalker implements Function<Stream<StackWalker.StackFrame>, StackWalker.StackFrame[]> {

        private final int stackDepth, startFrame;

        RawWalker(int stackDepth, int startFrame) {
            this.stackDepth = stackDepth;
            this.startFrame = startFrame;
        }

        @Override
        public StackWalker.StackFrame[] apply(Stream<StackWalker.StackFrame> stackFrameStream) {
            StackWalker.StackFrame[] elements = new StackWalker.StackFrame[stackDepth];
            Iterator<StackWalker.StackFrame> it = stackFrameStream.skip(startFrame).limit(stackDepth).iterator();
            int index = 0;
            while (it.hasNext()) {
                elements[index++] = it.next();
            }
            return elements;
        }
    }
  

    private class TransformingWalker implements Function<Stream<StackWalker.StackFrame>, StackWalker.StackFrame[]> {

        private final int stackDepth, startFrame;

        TransformingWalker(int stackDepth, int startFrame) {
            this.stackDepth = stackDepth;
            this.startFrame = startFrame;
        }

        @Override
        public StackFrameElement[] apply(Stream<StackWalker.StackFrame> stackFrameStream) {
            StackFrameElement[] elements = new StackWalker.StackFrame[stackDepth];
            Iterator<StackWalker.StackFrame> it = stackFrameStream.skip(startFrame).limit(stackDepth).iterator();
            int index = 0;
            while (it.hasNext()) {
                elements[index++] = it.next().toStackFrameElement();
            }
            return elements;
        }
    }
}

ThrowableExtraction.java

import org.openjdk.jmh.annotations.Benchmark;

public class ThrowableExtraction {

    private static Throwable call(int depth) {
        if (depth == 0) {
            return new Throwable();
        } else {
            return call(depth - 1);
        }
    }

    @Benchmark
    public Throwable snapshot() {
        return call(100);
    }

    @Benchmark
    public Object complete() {
        int stackDepth = 35, startFrame = 1;

        Throwable throwable = call(100);
      
        StackTraceElement[] source = throwable.getStackTrace();
        StackTraceElement[] copy = new StackTraceElement[Math.min(stackDepth, source.length - startFrame)];

        int sourceIndex = startFrame;
        int copyIndex = 0;
        while (sourceIndex < source.length && copyIndex < copy.length) {
            copy[copyIndex++] = source[sourceIndex++];
        }
        return copy;
    }
}

ThrowableSecretExtraction.java

import org.openjdk.jmh.annotations.Benchmark;

public class ThrowableSecretExtraction {
  
   static final JavaLangAccess JAVA_LANG_ACCESS = SharedSecrets.getJavaLangAccess();

    private static Throwable call(int depth) {
        if (depth == 0) {
            return new Throwable();
        } else {
            return call(depth - 1);
        }
    }

    @Benchmark
    public Throwable snapshot() {
        return call(100);
    }

    @Benchmark
    public Object complete() {
        int stackDepth = 35, startFrame = 1;

        Throwable throwable = call(100);
      
        int length = JAVA_LANG_ACCESS.getStackTraceDepth(throwable);
        StackTraceElement[] copy = new StackTraceElement[Math.min(stackDepth, source.length - startFrame)];

        int sourceIndex = startFrame;
        int copyIndex = 0;
        while (sourceIndex < length && copyIndex < copy.length) {
            copy[copyIndex++] = JAVA_LANG_ACCESS.getStackTraceElement(throwable, sorceIndex++);
        }
        return copy;
    }
}