多线程环境下，或者web环境下，可以使用ThreadLocal做变量池用

import java.util.HashMap;
import java.util.Map;

public abstract class AbstractThreadContext {
    public AbstractThreadContext() {
    }

    abstract ThreadLocal<Map<String, Object>> getThreadContext();

    public void set(final String key, final Object value) {
        ThreadLocal<Map<String, Object>> threadContext = this.getThreadContext();
        Map<String, Object> map = (Map)threadContext.get();
        if (map == null) {
            map = new HashMap();
        }

        ((Map)map).put(key, value);

        threadContext.set(map);
    }

    public void removeKey(String key) {
        ThreadLocal<Map<String, Object>> threadContext = this.getThreadContext();
        Map<String, Object> map = (Map)threadContext.get();
        if (map == null) {
            map = new HashMap();
        }

        ((Map)map).remove(key);
        threadContext.set(map);
    }

    public Object get(String key) {
        ThreadLocal<Map<String, Object>> threadContext = this.getThreadContext();
        Map<String, Object> map = (Map)threadContext.get();
        return map == null ? null : map.get(key);
    }

    public void clean() {
        ThreadLocal<Map<String, Object>> threadContext = this.getThreadContext();
        Map<String, Object> map = (Map)threadContext.get();
        if (map != null) {
            map.clear();
            threadContext.set(map);
        }

    }
}

import java.util.Map;

public final class ThreadContextStoreUtil extends AbstractThreadContext {
    private static ThreadLocal<Map<String, Object>> threadContext = new ThreadLocal();
    private static volatile ThreadContextStoreUtil app = null;

    private ThreadContextStoreUtil() {
    }

    public static synchronized ThreadContextStoreUtil getInstance() {
        if (app == null) {
            Class var0 = ThreadContextStoreUtil.class;
            synchronized(ThreadContextStoreUtil.class) {
                if (app == null) {
                    app = new ThreadContextStoreUtil();
                }
            }
        }

        return app;
    }

    @Override
    protected ThreadLocal<Map<String, Object>> getThreadContext() {
        return threadContext;
    }
}

public class ThreadMain {

    public static void main(String[] args) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                ThreadContextStoreUtil.getInstance().set("1", "1");
                ThreadContextStoreUtil.getInstance().set("2", "11");
                ThreadContextStoreUtil.getInstance().set("3", "111");
                System.out.println(Thread.currentThread().getName() + ThreadContextStoreUtil.getInstance().get("1"));
                System.out.println(Thread.currentThread().getName() + ThreadContextStoreUtil.getInstance().get("2"));
                System.out.println(Thread.currentThread().getName() + ThreadContextStoreUtil.getInstance().get("3"));
            }
        }, "a").start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                ThreadContextStoreUtil.getInstance().set("1", "2");
                ThreadContextStoreUtil.getInstance().set("2", "22");
                ThreadContextStoreUtil.getInstance().set("3", "222");
                System.out.println(Thread.currentThread().getName() + ThreadContextStoreUtil.getInstance().get("1"));
                System.out.println(Thread.currentThread().getName() + ThreadContextStoreUtil.getInstance().get("2"));
                System.out.println(Thread.currentThread().getName() + ThreadContextStoreUtil.getInstance().get("3"));
            }
        }, "b").start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                ThreadContextStoreUtil.getInstance().set("1", "3");
                ThreadContextStoreUtil.getInstance().set("2", "33");
                ThreadContextStoreUtil.getInstance().set("3", "333");
                System.out.println(Thread.currentThread().getName() + ThreadContextStoreUtil.getInstance().get("1"));
                System.out.println(Thread.currentThread().getName() + ThreadContextStoreUtil.getInstance().get("2"));
                System.out.println(Thread.currentThread().getName() + ThreadContextStoreUtil.getInstance().get("3"));
            }
        }, "c").start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                ThreadContextStoreUtil.getInstance().set("1", "4");
                ThreadContextStoreUtil.getInstance().set("2", "44");
                ThreadContextStoreUtil.getInstance().set("3", "444");
                System.out.println(Thread.currentThread().getName() + ThreadContextStoreUtil.getInstance().get("1"));
                System.out.println(Thread.currentThread().getName() + ThreadContextStoreUtil.getInstance().get("2"));
                System.out.println(Thread.currentThread().getName() + ThreadContextStoreUtil.getInstance().get("3"));
            }
        }, "d").start();



    }
}