StringBuilder 根据索引输出？

Question

如果第一个输入是 "Dog"，第二个是 "Wolf"，第三个是 "Cat"。结果如下：

Dog | Wolf | Wolf | Cat | Cat | Cat |

我的 forloop 是否导致它迭代过于频繁？

public class LabTextManipulation {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        ArrayList<String> parks = new ArrayList<String>();
        String enteredPark;
        StringBuilder sb = new StringBuilder();
        boolean stop = true;
        while (stop == true) {
            System.out.println("Please enter your favorite National Park or Done to stop: ");
            enteredPark = input.nextLine();
            if (!"Done".equalsIgnoreCase(enteredPark)) {
                parks.add(new String(enteredPark));
                for (int i = 0; i < parks.size(); i++) {
                    sb.append(enteredPark + " | ");
                }//end for
            } else {
                stop = false;
            }
        }

        String nationalParks = sb.toString();
        System.out.println(nationalParks);
    }
}

预计：

" Dog | Wolf | Cat |"

实际：

" Dog | Wolf | Wolf | Cat | Cat | Cat |"

Answer 1

这是导致问题的原因

for(int i = 0;i < parks.size(); i++ ) {
    sb.append(enteredPark + " | ");
}

每次向 parks 添加新字符串时，您都会在下一次迭代中增加添加到 sb 的重复值的计数 - 我相信您根本不应该使用循环

if(!"Done".equalsIgnoreCase(enteredPark)) {
    parks.add(enteredPark); // also don't create new String here
    sb.append(enteredPark + " | ");
}

StringBuilder 根据索引输出？

StringBuilder outputting according to index?

java

tostring

stringbuilder