//虚拟机配置了相关的最大缓存  -XX:AutoBoxCacheMax=1000Class
     clazz = Class.forName("java.lang.Integer$IntegerCache");Field f = clazz.getDeclaredField("cache");f.setAccessible(true);System.out.println(Arrays.toString((Integer[])f.get("cache")));f.setAccessible(false);//-XX:AutoBoxCacheMax=1000Integer i = 800;Integer j = 800;System.out.println(i == j);

java.lang.Integer$IntegerCache 

private static class IntegerCache {        static final int high;        static final Integer cache[];        static {            final int low = -128;            // high value may be configured by property            int h = 127;            if (integerCacheHighPropValue != null) {                // Use Long.decode here to avoid invoking methods that                // require Integer's autoboxing cache to be initialized                int i = Long.decode(integerCacheHighPropValue).intValue();                i = Math.max(i, 127);                // Maximum array size is Integer.MAX_VALUE                h = Math.min(i, Integer.MAX_VALUE - -low);            }            high = h;            cache = new Integer[(high - low) + 1];            int j = low;            for(int k = 0; k < cache.length; k++)                cache[k] = new Integer(j++);        }        private IntegerCache() {}    }

private static class ShortCache {        private ShortCache(){}        static final Short cache[] = new Short[-(-128) + 127 + 1];        static {            for(int i = 0; i < cache.length; i++)                cache[i] = new Short((short)(i - 128));        }    }

private static class LongCache {        private LongCache(){}        static final Long cache[] = new Long[-(-128) + 127 + 1];        static {            for(int i = 0; i < cache.length; i++)                cache[i] = new Long(i - 128);        }    }