1つの文字列の同じ指定長さ間隔に指定した文字列を挿入

	
	/**
	 *                        
	 * 
	 * @param target         
	 * 
	 * @param size     
	 * 
	 * @param insert       ，    "
"
	 * @return
	 */
	public static String collapseString(String target, int size, String insert){
		
		if(StringUtils.isEmpty(target)) return target; //       ，       
		
		int target_length = target.length();
		
		if(target_length <= size) return target; //              ，        
		
		insert = StringUtils.isEmpty(insert) ? "
" : insert;
		
		//    
		int times = 0;
		if(target_length % size == 0){
			times = target_length / size - 1;
		}else{
			times = target_length / size;
		}
		
		//     
		char [] result_chars = new char[target_length + times];
		
		//     
		char [] target_chars = new char[target_length];
		
		//             
		target.getChars(0, target_length, target_chars, 0);
		
		//       ，          
		int j = 0;
		for(int i = 0; i < target_chars.length; i++){
			
			//      
			if(i > 0 && i % size == 0){
				result_chars[j] = '`';
				j = j + 1;
			}
			
			result_chars[j] = target_chars[i];
			j = j + 1;
		}
		
		String resultStr = new String(result_chars);
		return resultStr.replaceAll("`", insert);
	}
	
	public static void main(String[] args) {
		//    ：            
		System.out.println(collapseString("AAAAAAAAA", 5, "_"));
	}