阅读kvstore\ArrayWrappers.java(1)

用来包装数组对象，将数组对象包装成一个能够比较的东东。

class ArrayWrappers {

  public static Comparable<Object> forArray(Object a) {}

  private static class ComparableIntArray implements Comparable<ComparableIntArray> {}

  private static class ComparableLongArray implements Comparable<ComparableLongArray> {}

  private static class ComparableByteArray implements Comparable<ComparableByteArray> {}

  private static class ComparableObjectArray implements Comparable<ComparableObjectArray> {}

}

　　看看测试代码怎么用的。

public class ArrayWrappersSuite {

  @Test
  public void testGenericArrayKey() {
   byte[] b1 = new byte[] { 0x01, 0x02, 0x03 };
   byte[] b2 = new byte[] { 0x01, 0x02 };
   int[] i1 = new int[] { 1, 2, 3 };
   int[] i2 = new int[] { 1, 2 };
   String[] s1 = new String[] { "1", "2", "3" };
   String[] s2 = new String[] { "1", "2" };

　　// 这里主要使用 ArrayWrappers.forArray() 函数， 得到一个Comparable<Object>对象 得到的对象可以用来比较
　　// 类型和值都一样才会比较成功
   assertEquals(ArrayWrappers.forArray(b1), ArrayWrappers.forArray(b1));
   assertNotEquals(ArrayWrappers.forArray(b1), ArrayWrappers.forArray(b2));
   assertNotEquals(ArrayWrappers.forArray(b1), ArrayWrappers.forArray(i1));  
   // 虽然都是1,2,3 但是类型不一样 
   assertNotEquals(ArrayWrappers.forArray(b1), ArrayWrappers.forArray(s1));  

   assertEquals(ArrayWrappers.forArray(i1), ArrayWrappers.forArray(i1));
   assertNotEquals(ArrayWrappers.forArray(i1), ArrayWrappers.forArray(i2));
   assertNotEquals(ArrayWrappers.forArray(i1), ArrayWrappers.forArray(b1));
   assertNotEquals(ArrayWrappers.forArray(i1), ArrayWrappers.forArray(s1));

   assertEquals(ArrayWrappers.forArray(s1), ArrayWrappers.forArray(s1));
   assertNotEquals(ArrayWrappers.forArray(s1), ArrayWrappers.forArray(s2));
   assertNotEquals(ArrayWrappers.forArray(s1), ArrayWrappers.forArray(b1));
   assertNotEquals(ArrayWrappers.forArray(s1), ArrayWrappers.forArray(i1));

   assertEquals(0, ArrayWrappers.forArray(b1).compareTo(ArrayWrappers.forArray(b1))); 
   assertTrue(ArrayWrappers.forArray(b1).compareTo(ArrayWrappers.forArray(b2)) > 0); //两个不同的数组比大小  {1,2,3} 比 {1，2}要大

   assertEquals(0, ArrayWrappers.forArray(i1).compareTo(ArrayWrappers.forArray(i1)));
   assertTrue(ArrayWrappers.forArray(i1).compareTo(ArrayWrappers.forArray(i2)) > 0);

   assertEquals(0, ArrayWrappers.forArray(s1).compareTo(ArrayWrappers.forArray(s1)));
   assertTrue(ArrayWrappers.forArray(s1).compareTo(ArrayWrappers.forArray(s2)) > 0);
  }

}

　　assertEquals是怎么做比较的？

       所以 forArray返回的 Comparable<Object> 这个对象肯定对 equals函数做了重构，这样数组返回的对象比较时候使用的是自己重构后的equals方法