JavaCC と ASM

public class Hello {
    public static void main(String[] args) throws Exception {
        System.out.println("Hello world");
    }
}

package com.tiqwab.example.asm;

import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.util.TraceClassVisitor;

import java.io.File;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.nio.file.Files;
import java.nio.file.Paths;

public class HelloWorld {

    /* カレントディレクトリに 'hello ASM' を出力する HelloAsm.class を作成する */
    public static void main(String[] args) throws Exception {
        final String classFileName = "HelloAsm.class";
        final String jbcTextFileName = "HelloAsm.txt";
        final String className = "HelloAsm";

        final int flag = ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES;
        // (1)
        ClassWriter cw = new ClassWriter(flag);
        // (2)
        cw.visit(
                Opcodes.V1_8,
                Opcodes.ACC_PUBLIC | Opcodes.ACC_SUPER,
                className,
                null,
                "java/lang/Object",
                null
                );

        // For constructor
        visitConstructor(cw);
        // For main
        visitMain(cw);

        // (4)
        byte[] bin = cw.toByteArray();
        // Output as text
        try (OutputStream os = new FileOutputStream(new File(jbcTextFileName));
             PrintWriter pw = new PrintWriter(os)){
            new ClassReader(bin).accept(new TraceClassVisitor(pw), 0);
        }
        // Output as binary
        // (5)
        Files.write(Paths.get(classFileName), bin);
    }

    /* コンストラクタの生成 */
    private static void visitConstructor(ClassWriter cw) {
        // (3)
        MethodVisitor mv = cw.visitMethod(
                Opcodes.ACC_PUBLIC,
                "<init>",
                "()V",
                null,
                null
        );
        mv.visitCode();
        mv.visitVarInsn(Opcodes.ALOAD, 0);
        mv.visitMethodInsn(
                Opcodes.INVOKESPECIAL,
                "java/lang/Object",
                "<init>",
                "()V",
                false
        );
        mv.visitInsn(Opcodes.RETURN);
        mv.visitMaxs(0,0);
        mv.visitEnd();
    }

    /* main メソッドの生成 */
    private static void visitMain(ClassWriter cw) {
        MethodVisitor mv = cw.visitMethod(
                Opcodes.ACC_PUBLIC | Opcodes.ACC_STATIC,
                "main",
                "([Ljava/lang/String;)V",
                null,
                null
        );
        mv.visitCode();
        mv.visitFieldInsn(
                Opcodes.GETSTATIC,
                "java/lang/System",
                "out",
                "Ljava/io/PrintStream;"
        );
        mv.visitLdcInsn("hello ASM");
        mv.visitMethodInsn(
                Opcodes.INVOKEVIRTUAL,
                "java/io/PrintStream",
                "println",
                "(Ljava/lang/String;)V",
                false
        );
        mv.visitInsn(Opcodes.RETURN);
        mv.visitMaxs(0,0);
        mv.visitEnd();
    }

}

// (1)
final int flag = ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES;
ClassWriter cw = new ClassWriter(flag);
...
MethodVisitor mv = cw.visitMethod(...);
mv.visitCode();
...
// (2)
mv.visitMaxs(0,0);