Main.java

package com.demonwav.stupid;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

public class Main {

    public static final Object object = new Object() {
        private final Object one = "one";
        private final Object two = "two";
        private final Object three = "three";
        private final Object four = "four";
        private final Object five = "five";
        private final Object six = "six";
        private final Object seven = "seven";
        private final Object eight = "eight";
        private final Object nine = "nine";
        private final Object ten = "ten";

        private void printFields() throws Throwable {
            forMethod(
                getField(Class.forName("java.lang.System"), "out"),
                "println", Class.forName("java.lang.String")
            ).call(
                one + ", " +
                    two + ", " +
                    three + ", " +
                    four + ", " +
                    five + ", " +
                    six + ", " +
                    seven + ", " +
                    eight + ", " +
                    nine + ", " +
                    ten
            );
        }
    };


    public static void main(String[] args) throws Throwable {
        final Class<?> scannerClass = Class.forName("java.util.Scanner");

        final Class<?> classArray = Class.forName("java.lang.reflect.Array");

        final Object classArrayObject = forMethod(
            classArray,
            "newInstance",
            Class.forName("java.lang.Class"),
            int.class
        ).call(Class.forName("java.lang.Class"), 1);

        final Object classArrayClass = forMethod(classArrayObject, "getClass").call();

        forMethod(
            Class.forName("java.lang.reflect.Array"),
            "set",
            Class.forName("java.lang.Object"),
            int.class,
            Class.forName("java.lang.Object")
        ).call(classArrayObject, 0, Class.forName("java.io.InputStream"));

        final Object constructor = forMethod((Object) scannerClass, "getConstructor", (Class<?>) classArrayClass).call(classArrayObject);

        final Class<?> array = Class.forName("java.lang.reflect.Array");
        final Object arrayObject = forMethod(
            array,
            "newInstance",
            Class.forName("java.lang.Class"),
            int.class
        ).call(Class.forName("java.lang.Object"), 1);

        final Object arrayClass = forMethod(arrayObject, "getClass").call();

        forMethod(
            Class.forName("java.lang.reflect.Array"),
            "set",
            Class.forName("java.lang.Object"),
            int.class,
            Class.forName("java.lang.Object")
        ).call(arrayObject, 0, getField(Class.forName("java.lang.System"), "in"));
        forMethod(constructor, "newInstance", (Class<?>) arrayClass).call(arrayObject);
        final Object scanner = forMethod(constructor, "newInstance", (Class<?>) arrayClass).call(arrayObject);

        while (true) {
            forMethod(getField(Class.forName("java.lang.System"), "out"), "print", Class.forName("java.lang.String"))
                .call("(S)et field / (G)et field / (C)all method / (Q)uit: ");
            final Object line = forMethod(scanner, "nextLine").call();
            forMethod(getField(Class.forName("java.lang.System"), "out"), "println").call();

            final Object lowerCase = forMethod(line, "toLowerCase").call();

            if (lowerCase.equals("q")) {
                forMethod(forMethod(Class.forName("java.lang.Runtime"), "getRuntime").call(), "exit", int.class).call(0);
            } else if (lowerCase.equals("s")) {
                forMethod(getField(Class.forName("java.lang.System"), "out"), "print", Class.forName("java.lang.String"))
                    .call("<fieldName>,<value>: ");
                final Object nextLine = forMethod(scanner, "nextLine").call();
                forMethod(getField(Class.forName("java.lang.System"), "out"), "println").call();

                final Object split = forMethod(nextLine, "split", Class.forName("java.lang.String")).call(",");
                final Object first = forMethod(
                    Class.forName("java.lang.reflect.Array"),
                    "get",
                    Class.forName("java.lang.Object"),
                    int.class
                ).call(split, 0);

                final Object second = forMethod(
                    Class.forName("java.lang.reflect.Array"),
                    "get",
                    Class.forName("java.lang.Object"),
                    int.class
                ).call(split, 1);

                setField(object, (String) first, second);
            } else if (lowerCase.equals("g")) {
                forMethod(getField(Class.forName("java.lang.System"), "out"), "print", Class.forName("java.lang.String"))
                    .call("<fieldName>: ");
                final Object nextLine = forMethod(scanner, "nextLine").call();
                forMethod(getField(Class.forName("java.lang.System"), "out"), "println").call();

                final Object field = getField(object, (String) nextLine);
                forMethod(getField(Class.forName("java.lang.System"), "out"), "println", Class.forName("java.lang.String"))
                    .call(field);
            } else if (lowerCase.equals("c")) {
                forMethod(getField(Class.forName("java.lang.System"), "out"), "print", Class.forName("java.lang.String"))
                    .call("<methodName>: ");
                final Object nextLine = forMethod(scanner, "nextLine").call();
                forMethod(getField(Class.forName("java.lang.System"), "out"), "println").call();
                forMethod(object, (String) nextLine).call();
            }
        }
    }




    //****************************************************************************************
    // Framework
    //****************************************************************************************
    public static class MethodCaller {
        private final Class<?> aClass;
        private final Object object;
        private final String method;
        private final Class<?>[] types;

        public MethodCaller(Class<?> aClass, Object object, String method, Class<?>[] types) throws Throwable {
            this.aClass = aClass;
            this.object = object;
            this.method = method;
            this.types = types;
        }

        public Object call(Object... params) throws Throwable {
            Method method;
            try {
                method = aClass.getDeclaredMethod(this.method, types);
            } catch (NoSuchMethodException e) {
                method = aClass.getMethod(this.method, types);
            }
            method.setAccessible(true);
            return method.invoke(object, params);
        }
    }

    public static MethodCaller forMethod(Class<?> aClass, String method, Class<?>... types) throws Throwable {
        return new MethodCaller(aClass, null, method, types);
    }

    public static MethodCaller forMethod(Object object, String method, Class<?>... types) throws Throwable {
        final Class<?> aClass = object.getClass();
        return new MethodCaller(aClass, object, method, types);
    }

    public static Object getField(Class<?> aClass, String fieldName) throws Throwable {
        Field field;
        try {
            field = aClass.getDeclaredField(fieldName);
        } catch (NoSuchFieldException e) {
            field = aClass.getField(fieldName);
        }
        field.setAccessible(true);
        return field.get(null);
    }

    public static Object getField(Object object, String fieldName) throws Throwable {
        final Class<?> aClass = object.getClass();
        Field field;
        try {
            field = aClass.getDeclaredField(fieldName);
        } catch (NoSuchFieldException e) {
            field = aClass.getField(fieldName);
        }
        field.setAccessible(true);
        return field.get(object);
    }

    public static Object setField(Class<?> aClass, String fieldName, Object value) throws Throwable {
        Field field;
        try {
            field = aClass.getDeclaredField(fieldName);
        } catch (NoSuchFieldException e) {
            field = aClass.getField(fieldName);
        }
        field.setAccessible(true);
        if (Modifier.isFinal(field.getModifiers())) {
            final Field modifiers = field.getClass().getDeclaredField("modifiers");
            modifiers.setAccessible(true);
            modifiers.setInt(field, field.getModifiers() & ~Modifier.FINAL);
        }
        final Object oldVal = getField(aClass, fieldName);
        field.set(null, value);
        return oldVal;
    }

    public static Object setField(Object object, String fieldName, Object value) throws Throwable {
        final Class<?> aClass = object.getClass();
        Field field;
        try {
            field = aClass.getDeclaredField(fieldName);
        } catch (NoSuchFieldException e) {
            field = aClass.getField(fieldName);
        }
        field.setAccessible(true);
        if (Modifier.isFinal(field.getModifiers())) {
            final Field modifiers = field.getClass().getDeclaredField("modifiers");
            modifiers.setAccessible(true);
            modifiers.setInt(field, field.getModifiers() & ~Modifier.FINAL);
        }
        final Object oldVal = getField(object, fieldName);
        field.set(object, value);
        return oldVal;
    }
}