如何检查String是否包含多次相同的字母？

Question

I'm a bit confused in how I would check if a String contains the same letter more than once.

ArrayList<String> words = new ArrayList<String>();

words.add("zebra");
words.add("buzzer");
words.add("zappaz");

Let's say I only want to print out any words which contain more than one "z", therefore only "buzzer" and "zappaz" would get printed. How would I do this?

Answer 1

要测试字符串是否包含两个z，您可以执行以下操作：

 boolean ok = word.matches(".*z.*z.*")

Answer 2

indexOf returns the... index of... a character in a string. It also takes an optional argument specifying where to search. If there is no match, it returns -1 . So just use it twice:

s.indexOf(letter, s.indexOf(letter) + 1) > -1

It works!

(For efficiency's sake, though, may as well check the first result .)

Answer 3

A smart solution could be, removing the character you want to search and compare the length of the resulting string with the complete string.

ArrayList<String> words = new ArrayList<String>();

words.add("zebra");
words.add("buzzer");
words.add("zappaz");

for (String word : words) {
  // calculate the length difference
  if (word.length() - word.replace("z", "").length() > 1) {
    System.out.println(word);
  }
}

will print:

buzzer
zappaz

Not very efficient, but it works and is pretty simple.

Answer 4

public static void main(String[] args) {

  String s = "bazzer";
  String news = s.replaceAll("z", "");

    if(news.length() < s.length() -1 ){
        System.out.println(s);
    }

  }