public StrBuilder del(int start, int end) throws StringIndexOutOfBoundsException {
		if (start < 0) {
			start = 0;
		}

		if (end >= this.position) {
			// end在边界及以外，相当于删除后半部分
			this.position = start;
			return this;
		} else if (end < 0) {
			// start和end都为0的情况下表示删除全部
			end = 0;
		}

		int len = end - start;
		// 截取中间部分，需要将后半部分复制到删除的开始位置
		if (len > 0) {
			System.arraycopy(value, start + len, value, start, this.position - end);
			this.position -= len;
		} else if (len < 0) {
			throw new StringIndexOutOfBoundsException("Start is greater than End.");
		}
		return this;
	}
@Test
	public void delTest() {
		// 删除全部测试
		StrBuilder strBuilder = new StrBuilder("ABCDEFG");
		int length = strBuilder.length();
		StrBuilder builder = strBuilder.del(0, length);
		assertEquals("", builder.toString());
	}