关于java 数组的一些知识

ArrayUtil
  让数组的长度容量涨一个
   

private static Object copyArrayGrow1(Object array, Class newArrayComponentType) {
  if (array != null) {
     int arrayLength = Array.getLength(array); //获得数组的长度,array不是数组将报异常
     Object newArray = Array.newInstance(array.getClass().getComponentType(), arrayLength + 1);//根据类型创建一个数组
      //  getComponentType() --object representing the component type of an array, or null if the type is not an array 

     System.arraycopy(array, 0, newArray, 0, arrayLength); //复制数组
    return newArray;
   }
return Array.newInstance(newArrayComponentType, 1);
}

 给数组指定位置上设定值

  

        String[] joinedArray = (String[]) Array.newInstance(String.class, 10);
        Array.set(joinedArray, 0, "a");
        Array.set(joinedArray, 1, "b");
        Array.set(joinedArray, 2, "c");
        Array.set(joinedArray, 3, "d");
        Array.set(joinedArray, 4, "e");
        Array.set(joinedArray, 5, "f");
        Array.set(joinedArray, 6, "g");
        Array.set(joinedArray, 7, "h");
        Array.set(joinedArray, 8, "i");
        Array.set(joinedArray, 9, "j");
        for (int i = 0; i < joinedArray.length; i++) {
            System.out.println(joinedArray[i]);
        }

从原来数组中返回一个子集
   

        int newSize = endIndexExclusive - startIndexInclusive; //开始和结束节点
        Class type = array.getClass().getComponentType();  //数组包含的类型
        if (newSize <= 0) {
            return (Object[]) Array.newInstance(type, 0); 
        }
        Object[] subarray = (Object[]) Array.newInstance(type, newSize);//创建新数组
        System.arraycopy(array, startIndexInclusive, subarray, 0, newSize);//数组复制