this was not very much fun to write :(

FWState.java

package com.iansenne.fw;

import java.util.ArrayList;
import java.util.
        function.Consumer;
class FWStateHandler<T>{
    FWState<T>handle(String name, T value) {
        boolean exists = FWStateManager.current().has(name);
        if (exists) {
            return (FWState<T>) FWStateManager.current().get(name);
        } else {
            FWStateManager.current().set(name, new FWState(name, value));
            return (FWState<T>) FWStateManager.current().get(name);
        }
    }
}
public class FWState<T>{
    private ArrayList<Consumer<Boolean>>handlers = new ArrayList<>();
    private static FWStateHandler<Byte>byte_handler = new FWStateHandler<Byte>();
    private static FWStateHandler<Short>short_handler = new FWStateHandler<Short>();
    private static FWStateHandler<Integer>int_handler = new FWStateHandler<Integer>();
    private static FWStateHandler<Long>long_handler = new FWStateHandler<Long>();
    private static FWStateHandler<Float>float_handler = new FWStateHandler<Float>();
    private static FWStateHandler<Double>double_handler = new FWStateHandler<Double>();
    private static FWStateHandler<Character>char_handler = new FWStateHandler<Character>();
    private static FWStateHandler<String>string_handler = new FWStateHandler<String>();
    private static FWStateHandler<Boolean>bool_handler = new FWStateHandler<Boolean>();

    public static FWState<Byte>Byte(Byte value) {
        return FWState.byte_handler.handle(FWStateManager.getNextName(), value);
    }
    public static FWState<Short>Short(Short value) {
        return FWState.short_handler.handle(FWStateManager.getNextName(), value);
    }
    public static FWState<Integer>Integer(Integer value) {
        return FWState.int_handler.handle(FWStateManager.getNextName(), value);
    }
    public static FWState<Long>Long(Long value) {
        return FWState.long_handler.handle(FWStateManager.getNextName(), value);
    }
    public static FWState<Float>Float(Float value) {
        return FWState.float_handler.handle(FWStateManager.getNextName(), value);
    }
    public static FWState<Double>Double(Double value) {
        return FWState.double_handler.handle(FWStateManager.getNextName(), value);
    }
    public static FWState<Character>Character(Character value) {
        return FWState.char_handler.handle(FWStateManager.getNextName(), value);
    }
    public static FWState<String>String(String value) {
        return FWState.string_handler.handle(FWStateManager.getNextName(), value);
    }
    public static FWState<Boolean>Boolean(Boolean value) {
        return FWState.bool_handler.handle(FWStateManager.getNextName(), value);
    }

    public static class named {
        public static FWState<Byte>Byte(String name, Byte value) {
            return FWState.byte_handler.handle(name, value);
        }
        public static FWState<Short>Short(String name, Short value) {
            return FWState.short_handler.handle(name, value);
        }
        public static FWState<Integer>Integer(String name, Integer value) {
            return FWState.int_handler.handle(name, value);
        }
        public static FWState<Long>Long(String name, Long value) {
            return FWState.long_handler.handle(name, value);
        }
        public static FWState<Float>Float(String name, Float value) {
            return FWState.float_handler.handle(name, value);
        }
        public static FWState<Double>Double(String name, Double value) {
            return FWState.double_handler.handle(name, value);
        }
        public static FWState<Character>Character(String name, Character value) {
            return FWState.char_handler.handle(name, value);
        }
        public static FWState<String>String(String name, String value) {
            return FWState.string_handler.handle(name, value);
        }
        public static FWState<Boolean>Boolean(String name, Boolean value) {
            return FWState.bool_handler.handle(name, value);
        }

        public static FWState<Byte>Byte(String name) {
            return FWState.byte_handler.handle(name, null);
        }
        public static FWState<Short>Short(String name) {
            return FWState.short_handler.handle(name, null);
        }
        public static FWState<Integer>Integer(String name) {
            return FWState.int_handler.handle(name, null);
        }
        public static FWState<Long>Long(String name) {
            return FWState.long_handler.handle(name, null);
        }
        public static FWState<Float>Float(String name) {
            return FWState.float_handler.handle(name, null);
        }
        public static FWState<Double>Double(String name) {
            return FWState.double_handler.handle(name, null);
        }
        public static FWState<Character>Character(String name) {
            return FWState.char_handler.handle(name, null);
        }
        public static FWState<String>String(String name) {
            return FWState.string_handler.handle(name, null);
        }
        public static FWState<Boolean>Boolean(String name) {
            return FWState.bool_handler.handle(name, null);
        }
    }
    String name;
    T value;
    public FWState(String name, T value) {
        this.name = name;
        this.value = value;
    }
    public T get() {
        return this.value;
    }
    public void set(T value) throws Exception {
        if (!this.value.equals(value)) {
            this.value = value;
            ArrayList<Consumer<Boolean>>handlers = this.handlers;
            this.handlers = new ArrayList<Consumer<Boolean>>();
            for (Consumer<Boolean>handler: handlers) {
                handler.accept(true);
            }
        }
    }
    public void watch(Consumer<Boolean>handler) {
        this.handlers.add(handler);
    }
    public void clearListeners() {
        this.handlers = new ArrayList<Consumer<Boolean>>();
    }
}