Java程式查詢字串的重複字元

<b>import</b> java.util.HashMap;
<b>import</b> java.util.Map;
<b>import</b> java.util.Scanner;
<b>import</b> java.util.Set;

<font><i>/**
* Java Program to find duplicate characters in String.
*
*
* @author http://java67.blogspot.com
*/</i></font><font>
<b>public</b> <b>class</b> FindDuplicateCharacters{

<b>public</b> <b>static</b> <b>void</b> main(String args[]) {
printDuplicateCharacters(</font><font>"Programming"</font><font>);
printDuplicateCharacters(</font><font>"Combination"</font><font>);
printDuplicateCharacters(</font><font>"Java"</font><font>);
}

</font><font><i>/*
* Find all duplicate characters in a String and print each of them.
*/</i></font><font>
<b>public</b> <b>static</b> <b>void</b> printDuplicateCharacters(String word) {
<b>char</b>[] <b>char</b>acters = word.toCharArray();

</font><font><i>// build HashMap with character and number of times they appear in String</i></font><font>
Map<Character, Integer> charMap = <b>new</b> HashMap<Character, Integer>();
<b>for</b> (Character ch : characters) {
<b>if</b> (charMap.containsKey(ch)) {
charMap.put(ch, charMap.get(ch) + 1);
} <b>else</b> {
charMap.put(ch, 1);
}
}

</font><font><i>// Iterate through HashMap to print all duplicate characters of String</i></font><font>
Set<Map.Entry<Character, Integer>> entrySet = charMap.entrySet();
System.out.printf(</font><font>"List of duplicate characters in String '%s' %n"</font><font>, word);
<b>for</b> (Map.Entry<Character, Integer> entry : entrySet) {
<b>if</b> (entry.getValue() > 1) {
System.out.printf(</font><font>"%s : %d %n"</font><font>, entry.getKey(), entry.getValue());
}
}
}

}

Output
List of duplicate characters in String 'Programming'
g : 2
r : 2
m : 2
List of duplicate characters in String 'Combination'
n : 2
o : 2
i : 2
List of duplicate characters in String 'Java'
</font>