我想打印除最后一个、最后两个、最后三个之外的所有字母

Question

我正在尝试打印这样的字符串：

cat

ca

c

但现在用我的代码，我只能得到

ttt

tt

t

代码

public static String bingo(String s) {

        int len = s.length();

        for(int i = 1; i <=s.length(); i++) {

            for(int k = 1; k <= s.length() - i+1; k++) {

                System.out.print(s.substring(len-5));

            }

            System.out.println();

        }

        return s;

    }

Answer 1

您可以从长度迭代到 1 并打印每行中的子字符串：public static void bingo(String s) {&nbsp; &nbsp; for (int i = s.length(); i > 0; i--) {&nbsp; &nbsp; &nbsp; &nbsp; System.out.println(s.substring(0, i));&nbsp; &nbsp; }}输出（对于猫）catcac

Answer 2

你快明白了！这就是可以用 来完成的方法while loop。public static String bingo(String s) {&nbsp; &nbsp; int index = s.length();&nbsp; &nbsp; while (index != 0)&nbsp; &nbsp; &nbsp; &nbsp; System.out.println(s.substring(0, index--));&nbsp; &nbsp; return s;}这是如何完成的for looppublic static String bingo(String s) {&nbsp; &nbsp; for (int i = s.length(); i != 0; i--)&nbsp; &nbsp; &nbsp; &nbsp; System.out.println(s.substring(0, i));&nbsp; &nbsp; return s;}

Answer 3

当然其他答案是正确的，但为什么不也以功能性的方式学习呢？// you can use the tails everywhere you need (require Java 9+)static Stream<String> tails(String xs) {&nbsp; &nbsp; return Stream.iterate(xs, x -> !x.isEmpty(), x -> x.substring(0, x.length() - 1));}// usage examplepublic static void main(String[] args) {&nbsp; &nbsp; tails("cat").forEach(System.out::println);}然而，这些参数是不言自明的（参见 javadoc iterate ）：.iterate(&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;// iterate&nbsp; &nbsp; &nbsp; &nbsp; xs,&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;// using `xs` as seed&nbsp; &nbsp; &nbsp; &nbsp; x -> !x.isEmpty(),&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; // as long as the condition is true&nbsp; &nbsp; &nbsp; &nbsp; x -> x.substring(0, x.length() - 1)&nbsp; &nbsp; &nbsp;// transform the current value);

Answer 4

public static String bingo(String s) {&nbsp; &nbsp; int len = s.length();&nbsp; &nbsp; for(int i = 0; i <s.length(); i++) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; System.out.println(s.substring(0,len-i));&nbsp; &nbsp; }&nbsp; &nbsp; return s;}