README.md

コンパイル

javac -cp $JAVA_HOME/lib/tools.jar MisoProcessor.java  
javac -processor MisoProcessor Miso.java  
java Miso 0  
# --> true

Related

• Java でもa == 1 && a == 2 && a == 3でtrueって出力させたい

Miso.java

public class Miso {

    public static void main(String... args){
        int n = Integer.parseInt(args[0]);
        if (n == 1 && n == 2 && n == 3) {
            System.out.println("true");
        } else {
            System.out.println("false");
        }
    }

}

MisoProcessor.java

import java.util.*;

import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.ProcessingEnvironment;
import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedAnnotationTypes;
import javax.annotation.processing.SupportedSourceVersion;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.TypeElement;

import com.sun.source.tree.*;
import com.sun.source.util.TreeScanner;
import com.sun.source.util.Trees;
import com.sun.tools.javac.model.JavacElements;
import com.sun.tools.javac.processing.JavacProcessingEnvironment;
import com.sun.tools.javac.tree.*;
import com.sun.tools.javac.tree.JCTree.JCIf;
import com.sun.tools.javac.tree.TreeMaker;


@SupportedSourceVersion(SourceVersion.RELEASE_8)
@SupportedAnnotationTypes("*")
public class MisoProcessor extends AbstractProcessor{

    @Override
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        JavacProcessingEnvironment env = (JavacProcessingEnvironment)processingEnv;
        roundEnv.getRootElements().stream()
            .forEach(e -> {
                System.err.println(e);
                Trees.instance(env)
                    .getPath(e)
                    .getCompilationUnit()
                    .accept(new Visitor(processingEnv, env), null);
            });
        return false;
    }

    private class Visitor extends TreeScanner<Void, Void> {
        JavacElements elements;
        TreeMaker maker;
        Visitor(ProcessingEnvironment processingEnv, JavacProcessingEnvironment env) {
            elements = JavacElements.instance(env.getContext());
            maker = TreeMaker.instance(env.getContext());
        }

        @Override
        public Void visitIf(IfTree arg0, Void ignore) {
            JCIf jcif = (JCIf) arg0;
            jcif.cond = maker.Literal(true);
            return null;
        }

    }
}