Java Integer类型比较

Integer a=10;
Integer b=10;
System.out.print(a==b);
Integer c=200;
Integer d=200;
System.out.print(c==d);

    public static Integer valueOf(int i) {
        if (i >= IntegerCache.low && i <= IntegerCache.high)//判断如果大于low或者小于high
            return IntegerCache.cache[i + (-IntegerCache.low)];//从这个cache中取出返回
        return new Integer(i);//返回新实例
    }

 private static class IntegerCache {
        static final int low = -128;
        static final int high;
        static final Integer cache[];

        static {
            // high value may be configured by property
            int h = 127;
            String integerCacheHighPropValue =
                sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");//获取jvm参数
            if (integerCacheHighPropValue != null) {
                try {
                    int i = parseInt(integerCacheHighPropValue);
                    i = Math.max(i, 127);//取两者最大值
                    // Maximum array size is Integer.MAX_VALUE
                    h = Math.min(i, Integer.MAX_VALUE - (-low) -1);//担心虚拟机数组过大判断了一下取两者最小值
                } catch( NumberFormatException nfe) {
                    // If the property cannot be parsed into an int, ignore it.
                }
            }
            high = h;

            cache = new Integer[(high - low) + 1];//创建数组
            int j = low;
            for(int k = 0; k < cache.length; k++)
                cache[k] = new Integer(j++);//第一步先将这个对象数组创建出来

            // range [-128, 127] must be interned (JLS7 5.1.7)
            assert IntegerCache.high >= 127;//Debug 断言一下
        }

        private IntegerCache() {}
    }