搞清楚一道关于Integer的面试题

public class IntegerDemo {
    public static void main(String[] args) {
        Integer a = 888;
        Integer b = 888;
        Integer c = 88;
        Integer d = 88;
        System.out.println(a == b);
        System.out.println(c == d);
    }
}

false
true

Integer a = 888;

Integer a = new Integer(888);

    //具体源码部分
    public static Integer valueOf(int i) {
        //i>=-128&&i<=127
        if (i >= IntegerCache.low && i <= IntegerCache.high)
            return IntegerCache.cache[i + (-IntegerCache.low)];
        return new Integer(i);
    }
    //Integer的静态内部类
    private static class IntegerCache {
        static final int low = -128;
        static final int high;
        //常量数组
        static final Integer cache[];

        static {
            // high value may be configured by property
            int h = 127 
            //省略无关代码....
            high = h;
            //初始化cache数组大小
            //cache的大小=127-（-128）+1=256
            cache = new Integer[(high - low) + 1];
            int j = low;
            for(int k = 0; k < cache.length; k++)
                //把-128到127的数字全部转换成Integer对象
                //并存入到cache数组中。
                cache[k] = new Integer(j++);
        } 
       private IntegerCache() {}
    }

public class IntegerDemo {
    public static void main(String[] args) {
        Integer a = new Integer(88);
        test(a);
        System.out.println(a);
    }
    private void test(Integer integer){
        integer=new Integer(99);
    }
}

public class IntegerDemo {
    public static void main(String[] args) {
        Integer a = new Integer(88);
        a = 99;
        System.out.println(a);
    }
}

public final class Integer extends Number implements Comparable<Integer> {
  //final修饰变量，如果是基本数据类型的变量，则其数值一旦在初始化之后便不能更改
  //如果是引用类型的变量，则在对其初始化之后便不能再让其指向另一个对象。
  private final int value;
  public Integer(int value) {
     this.value = value;
 }
}