HttpServlet中getAllDeclaredMethods()方法

 1  private static Method[] getAllDeclaredMethods(Class<?> c) {
 2 
 3         if (c.equals(javax.servlet.http.HttpServlet.class)) {
 4             return null;
 5         }
 6 
 7         Method[] parentMethods = getAllDeclaredMethods(c.getSuperclass());
 8         Method[] thisMethods = c.getDeclaredMethods();
 9 
10         if ((parentMethods != null) && (parentMethods.length > 0)) {
11             Method[] allMethods =
12                 new Method[parentMethods.length + thisMethods.length];
13             System.arraycopy(parentMethods, 0, allMethods, 0,
14                              parentMethods.length);
15             System.arraycopy(thisMethods, 0, allMethods, parentMethods.length,
16                              thisMethods.length);
17 
18             thisMethods = allMethods;
19         }
20 
21         return thisMethods;
22     }

one:if ((parentMethods != null) && (parentMethods.length > 0)) 

two:System.arraycopy(parentMethods, 0, allMethods, 0, parentMethods.length);

1 public static native void arraycopy(Object src,  int  srcPos,
2                                         Object dest, int destPos,
3                                         int length);

1      * @param      src      the source array. //原数组
2      * @param      srcPos   starting position in the source array. //原数组的起始位置
3      * @param      dest     the destination array.//目标数组
4      * @param      destPos  starting position in the destination data.//目标数组起始位置
5      * @param      length   the number of array elements to be copied.//需要复制的长度