1.实现一个类似于ConcurrentHashMap的分段加锁

import java.util.HashMap;import java.util.Map;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;public class SegmentLock {	private static final int DEFAULT_INITIAL_CAPACITY = 16;	private static final int MAXIMUM_CAPACITY = 1 << 30;	private static final int MAX_SEGMENTS = 1 << 16; // slightly conservative	final int segmentMask;	final int segmentShift;	private Pair
     
      >[] segmentLocks;	public SegmentLock(final int concurrentLevel) {		int size = 1;		int shift = 0;		while (size < concurrentLevel) {			size <<= 1;			shift += 1;		}		segmentMask = size;		segmentShift = 32 - shift;		for (int i = 0; i < size; i++) {			segmentLocks[i] = new Pair(new ReentrantLock(), new HashMap
      
       ());		}	}	public Pair
       
        > get(final String key) {		return segmentLocks[(hash(key.hashCode()) >> segmentShift) & segmentMask];	}	private static int hash(int h) {		h += (h << 15) ^ 0xffffcd7d;		h ^= (h >>> 10);		h += (h << 3);		h ^= (h >>> 6);		h += (h << 2) + (h << 14);		return h ^ (h >>> 16);	}	static class Pair
        
          {		private final Left left;		private final Right right;		public Pair(final Left left, final Right right) {			this.left = left;			this.right = right;		}	}	static class Counter {		private int count;		public int increaseAndGet() {			return ++count;		}		public int decreaseAndGet() {			return --count;		}		public int get() {			return count;		}	}}
        
       
      
     

　　

2.怎样初始化一个泛型数组？

   new ArrayList<String>[]();