如何检查特定字符串是否在另一个字符串中多次出现？

Question

我的代码从用户那里获取输入，如果有两个"bread"子字符串，则打印它们之间的字符串。例如，"breadjavabread"输出"java"。但是，当我的代码只有一个"bread"字符串时，会弹出一个错误。例如，"usjdbbreaddudub"。我该如何解决这个问题？

String cheese = "no bread";

String bread = "bread";

for (int i = 0; i < s.length() - 5; i++)

{

  String m = s.substring(i, i + 5);

  if (m.equals(bread))

  {

    cheese = s.substring(s.indexOf(bread) + bread.length(), s.lastIndexOf(bread));

  }

}

System.out.print(cheese);

Answer 1

有很多方法可以解决这个问题。这是其中的3个比较indexOf和lastIndexOfString cheese;String bread = "bread";int firstIndex = s.indexOf(bread);int lastIndex = s.lastIndexOf(bread);if (firstIndex == -1) {&nbsp; &nbsp; cheese = "no bread";} else if (lastIndex == firstIndex) {&nbsp; &nbsp; cheese = "only one bread";}cheese = s.substring(firstIndex + bread.length(), lastIndex);System.out.print(cheese);常用表达：Matcher m = Pattern.compile("bread(.+?)bread").matcher(s);if (m.find()) {&nbsp; &nbsp; System.out.println(m.group(1));} else {&nbsp; &nbsp; System.out.println("Not enough bread");}分裂：String[] parts = s.split("bread");if (parts.length == 3) {&nbsp; &nbsp; System.out.println(parts[1]);} else {&nbsp; &nbsp; System.out.println("Not enough or too much bread");}