java实现继承AbstractStateBackend类，实现CheckpointStorage和StateBackend接口中的方法，并在createKeyedStateBackend方法中返回一个自定义的KeyedStateBackend实现类，例如RedisKeyedStateBackend。在这个RedisKeyedStateBackend类中，你需要实现将状态存储到Redis中的逻辑，例如使用Jedis连接池连接Redis，并将状态序列化为JSON字符串存储到Redis中。

好的，你的问题是如何在Java中实现继承AbstractStateBackend类，实现CheckpointStorage和StateBackend接口中的方法，并在createKeyedStateBackend方法中返回一个自定义的KeyedStateBackend实现类，例如RedisKeyedStateBackend。

首先，你需要创建一个类，继承AbstractStateBackend，并实现CheckpointStorage和StateBackend接口中的方法。这些方法包括savepoint()、loadCheckpointMetadata()、dispose()、createKeyedStateBackend()等。在实现createKeyedStateBackend()方法时，你要返回一个自定义的KeyedStateBackend实现类，例如RedisKeyedStateBackend。

在RedisKeyedStateBackend类中，你需要实现将状态存储到Redis中的逻辑。你可以使用Jedis连接池连接Redis，并将状态序列化为JSON字符串存储到Redis中。可以使用以下代码实现：

public class RedisKeyedStateBackend<K> extends AbstractKeyedStateBackend<K> {
    private JedisPool pool;
    
    public RedisKeyedStateBackend(Environment env, TypeSerializer<K> keySerializer, int numberOfKeyGroups) throws Exception {
        super(env, keySerializer, numberOfKeyGroups);
        pool = new JedisPool(new JedisPoolConfig(), "localhost");
    }
    
    @Override
    public <N, S extends State, T> S createState(StateDescriptor<S, T> stateDescriptor) throws Exception {
        return null;
    }
    
    @Override
    public void dispose() throws Exception {
        pool.close();
    }
    
    @Override
    public CheckpointStorage createCheckpointStorage(JobID jobId) throws IOException {
        return null;
    }
    
    @Override
    public <N> Stream<K> getKeys(String state, N namespace) {
        return null;
    }
    
    @Override
    public <N, S extends State> S getState(StateDescriptor<S, ?> stateDescriptor) throws Exception {
        return null;
    }
    
    @Override
    public <N, S extends State> void releaseState(S state, Runnable postReleaseAction) throws Exception {
    }
    
    @Override
    public void restore(Collection<MasterState> masterStates) throws Exception {
    }
    
    @Override
    public void restore(Collection<StateObjectCollection<OperatorStateHandle>> keyedState, Collection<StateObjectCollection<OperatorStateHandle>> operatorState) throws Exception {
    }
    
    @Override
    public void snapshot(long checkpointId, long timestamp, CheckpointStreamFactory streamFactory, CheckpointOptions options) throws Exception {
    }
    
    @Override
    protected StateTable newStateTable(TypeSerializer<K> keySerializer, RegisteredKeyedBackendStateMetaInfo.Snapshot<?> metaInfo) {
        return null;
    }
    
    @Override
    public StateBackend getRawStateBackend() {
        return null;
    }
    
    @Override
    public InternalKvState<K, ?, ?> createInternalState(TypeSerializer<K> keySerializer, StateDescriptor<?, ?> stateDesc) throws Exception {
        return null;
    }
    
    @Override
    protected <N> StateTable<K, N, ? extends State> createStateTable(StateDescriptor<? extends State, ?> stateDesc) throws Exception {
        return null;
    }
    
    private Jedis getJedis() {
        return pool.getResource();
    }
    
    private void releaseJedis(Jedis jedis) {
        jedis.close();
    }
    
    private String getKeyByGroupAndKey(int groupIndex, Object key) {
        return groupIndex + "_" + key.toString();
    }
    
    private byte[] serializeState(Object state) throws IOException {
        ObjectMapper mapper = new ObjectMapper();
        return mapper.writeValueAsString(state).getBytes();
    }
    
    private Object deserializeState(byte[] bytes, Class<?> clazz) throws IOException {
        ObjectMapper mapper = new ObjectMapper();
        return mapper.readValue(bytes, clazz);
    }
    
    static class RedisState implements Serializable {
        public String value;
        
        public RedisState(String value) {
            this.value = value;
        }
    }
    
    class RedisKvState<N> implements InternalKvState<K, N, RedisState> {
        private final String stateName;
        private final TypeSerializer<N> namespaceSerializer;
        private final byte[] statePrefix;
        private final byte[] statePrefixGroup;
        
        public RedisKvState(
            String stateName,
            TypeSerializer<K> keySerializer,
            TypeSerializer<N> namespaceSerializer,
            int groupIndex) {
            this.stateName = stateName;
            this.namespaceSerializer = namespaceSerializer;
            String stateGroupPrefix = "state_" + stateName + "_" + groupIndex + "_";
            String statePrefix = stateGroupPrefix + "K_";
            this.statePrefix = statePrefix.getBytes();
            this.statePrefixGroup = stateGroupPrefix.getBytes();
        }
        
        @Override
        public void setCurrentNamespace(N namespace) {
        }
        
        @Override
        public byte[] getSerializedValue(K key, N namespace) throws Exception {
            String redisKey = getKeyByGroupAndKey(getGroupIndexForKey(key), key);
            try (Jedis jedis = getJedis()) {
                byte[] bytes = jedis.get(redisKey.getBytes());
                if (bytes != null) {
                    return bytes;
                }
            }
            return null;
        }
        
        @Override
        public void clear(K key, N namespace) throws Exception {
            String redisKey = getKeyByGroupAndKey(getGroupIndexForKey(key), key);
            try (Jedis jedis = getJedis()) {
                jedis.del(redisKey.getBytes());
            }
        }
        
        @Override
        public void setCurrentKey(K key) {
        }
        
        @Override
        public void remove(K key, N namespace) throws Exception {
            String redisKey = getKeyByGroupAndKey(getGroupIndexForKey(key), key);
            try (Jedis jedis = getJedis()) {
                jedis.del(redisKey.getBytes());
            }
        }
        
        @Override
        public void remove(K key, N namespace, long timestamp) throws Exception {
            remove(key, namespace);
        }
        
        @Override
        public void mergeNamespaces(N target, Collection<N> sources) throws Exception {
        }
        
        @Override
        public boolean contains(K key, N namespace) throws Exception {
            String redisKey = getKeyByGroupAndKey(getGroupIndexForKey(key), key);
            try (Jedis jedis = getJedis()) {
                return jedis.exists(redisKey.getBytes());
            }
        }
        
        @Override
        public Iterable<Map.Entry<N, RedisState>> getEntries(K key) throws Exception {
            List<Map.Entry<N, RedisState>> entries = new ArrayList<>();
            try (Jedis jedis = getJedis()) {
                Set<byte[]> keys = jedis.keys(statePrefix);
                for (byte[] keyBytes : keys) {
                    String groupAndKey = new String(keyBytes);
                    String[] groupAndKeyArray = groupAndKey.split("_");
                    int groupIndex = Integer.parseInt(groupAndKeyArray[2]);
                    if (getGroupIndexForKey(key) == groupIndex && groupAndKeyArray[3].equals(key.toString())) {
                        String value = jedis.get(keyBytes).toString();
                        RedisState state = new RedisState(value);
                        N namespace = namespaceSerializer.deserialize(jedis.get(groupAndKey.getBytes()));
                        entries.add(new SimpleEntry<>(namespace, state));
                    }
                }
            }
            return entries;
        }
        
        @Override
        public Iterable<K> getKeys(N namespace) throws Exception {
            List<K> keys = new ArrayList<>();
            try (Jedis jedis = getJedis()) {
                Set<byte[]> keysBytes = jedis.keys(statePrefixGroup);
                for (byte[] keyBytes : keysBytes) {
                    byte[] valueBytes = jedis.get(keyBytes);
                    K key = keySerializer.deserialize(keyBytes);
                    N ns = namespaceSerializer.deserialize(valueBytes);
                    if (ns.equals(namespace)) {
                        keys.add(key);
                    }
                }
            }
            return keys;
        }
        
        @Override
        public void put(K key, N namespace, RedisState state) throws Exception {
            String redisKey = getKeyByGroupAndKey(getGroupIndexForKey(key), key);
            try (Jedis jedis = getJedis()) {
                jedis.set(redisKey.getBytes(), serializeState(state));
                jedis.set((statePrefixGroup + redisKey).getBytes(), namespaceSerializer.serialize(namespace));
            }
        }
    }
}

在这个RedisKeyedStateBackend类中，我们定义了一个RedisKvState类，它实现了InternalKvState接口。在这个类中，我们使用Jedis连接池连接Redis，并将状态序列化为JSON字符串存储到Redis中。在getSerializedValue()方法中，我们根据key从Redis中获取序列化后的状态值。在put()方法中，我们将状态序列化为JSON字符串，并存储到Redis中。在getKeys()方法中，我们从Redis中获取所有的key，并返回它们的集合。