Class前的註釋就不翻譯了，對原始碼的設計說明有限。直接上程式碼：

1.  先看一下它的繼承、實現關係：

•     public final class Integer extends Number implements Comparable<Integer>

  
  
• Number是個抽象類，大概包含六個抽象方法，都是用來型別轉換的 具體程式碼如下：

1. public abstract class Number implements java.io.Serializable {
   
       public abstract int intValue();
   
       public abstract long longValue();
   
       public abstract float floatValue();
   
       public abstract double doubleValue();
   
       public byte byteValue() {
           return (byte)intValue();
       }
   
       public short shortValue() {
           return (short)intValue();
       }
   
       /** use serialVersionUID from JDK 1.0.2 for interoperability */
       private static final long serialVersionUID = -8742448824652078965L;
   }
    
   

           這就是繼承後 子類的實現，強轉。

    public long longValue() {
           return (long)value;
       }

   •         看下Comparable 介面，只有一個compareTo 比較大小方法：

    public int compareTo(T o);    

               看下Integer的具體        

     public int compareTo(Integer anotherInteger) {
           return compare(this.value, anotherInteger.value);
       }
   
       public static int compare(int x, int y) {
           return (x < y) ? -1 : ((x == y) ? 0 : 1);
    
   
       }
      

         如果看程式碼有點費勁，那複製如下程式碼，自己執行下看結果就懂了。
           

   public class Test {
   	public static void main(String[] args) {
   		Integer it1=128;
   		Integer it2=-128;
   		Integer it3=128;
   		System.out.println(it2.compareTo(it1)+"-----x < y");
   		System.out.println(it1.compareTo(it2)+"------x > y");
   		System.out.println(Integer.compare(it1,it3)+"-----x == y");
   		
   	}
   }
    
   

   
          列印結果：

   -1-----x < y
   1------x > y
   0-----x == y

   
   

2.   Integer的快取問題

            Integer預設放入快取的區間是-128 至127 。但最大快取值可以手動調整，請看：

        The Javadoc comment clearly states that this class is for cache and to support the autoboxing of values between 128 and 127. The high value of 127 can be modified by using a VM argument -XX:AutoBoxCacheMax=size. So the caching happens in the for-loop. It just runs from the low to high and creates as many Integer instances and stores in an Integer array named cache. As simple as that. This caching is doing at the first usage of the Integer class. Henceforth, these cached instances are used instead of creating a new instance (during autoboxing).

public class IntegerTest {
	public static void main(String[] args) {
		Integer it1=2008;
		Integer it2=2008;
		System.out.println(it1==it2);//true 說明：為啥超了127了還是true呢？因為我設定了vm arguments引數 -XX:AutoBoxCacheMax=2008
		Integer it1t=2009;
		Integer it2t=2009;
		System.out.println(it1t==it2t);//false 說明：超過 2008  false了吧~~
		Integer newit1=new Integer(127);
		Integer newit2=new Integer(127);
		System.out.println(newit1==newit2);//false 說明：New的話是在heap上佔用獨立記憶體的新物件
		int it3=127;
		int it4=127;
		int it5=2008;
		System.out.println(it3==it4);//true
		System.out.println(it1==it5);//true
	}
}

true
false
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            凌晨了，有時間再記~睡覺。