strbuf.delete(2, strbuf.length()); //这句话是什么意思

Question

public void addCards(){         String[] color ={"黑桃","红桃","梅花","方片"};         String[] num = {"2","3","4","5","6","7","8","9","10","J","Q","K","A"};         int c =0;         System.out.println("------------创建扑克牌-------------");         for(int i = 0; i < 4; i++)         {                         StringBuffer strbuf=new StringBuffer();              strbuf .append(color[i]);              for(int  j = 0; j < 13; j++){                 strbuf.insert(2, num[j]);                 Cards card = new Cards();                 card.name = strbuf.toString();                 cardsToSelect.add(c, card);                 c++;                 strbuf.delete(2, strbuf.length()); //这句话是什么意思             }          }         System.out.println("----------扑克牌创建成功！---------------");         for (Cards card : cardsToSelect) {             System.out.print(card.name+",");         }             System.out.println();      }