public StrBuilder del(int start, int end) {
		if (start < 0) {
			start = 0;
		}
		if (end > this.position) {
			end = this.position;
		}
		if (start > end) {
			throw new StringIndexOutOfBoundsException("Start is greater than End.");
		}
		if (end == this.position) {
			this.position = start;
		}

		int len = end - start;
		if (len > 0) {
			System.arraycopy(value, start + len, value, start, this.position - end);
			this.position -= len;
		}
		return this;
	}
public StrBuilder del ( int start , int end ) { if ( start < 0 ) { start = 0 ; } if ( end > this . position ) { end = this . position ; } if ( start > end ) { throw new StringIndexOutOfBoundsException ( "Start is greater than End." ) ; } if ( end == this . position ) { this . position = start ; } int len = end - start ; if ( len > 0 ) { System . arraycopy ( value , start + len , value , start , this . position - end ) ; this . position -= len ; } return this ; }
删除指定长度的字符

@param start 开始位置（包括）
@param end 结束位置（不包括）
@return this