Question

java查询一个字符串中重复的字符

例:String str = "abcdaebijkd";
查找出来就应为:a,b,d

Answer 1

1:
public static List<Character> test(String str) {
Set<Character> set = new HashSet<Character>();
List<Character> list = new ArrayList<Character>();
for(int i=0;i<str.length();i++){
char c = str.charAt(i);
boolean has = set.contains(c);
if(has){
list.add(c);
}
else{
set.add(c);
}
}
return list;
}
只写了一个方法，供参考。

2:
import java.util.ArrayList;
public class Test {
public static void main(String[] args) {
String s = "abcdaebijkd";
ArrayList list = new ArrayList();
for(int i=0; i<s.length(); i++){
char c = s.charAt(i);
if(s.indexOf(c,i+1)>-1){
Character ch = new Character(c);
if(!list.contains(ch))
list.add(ch);
}
}
for(int i=0; i<list.size(); i++)
System.out.print(list.get(i)+",");
}
}

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Answer 2

试试这个
import java.util.ArrayList;
public class Test {
public static void main(String[] args) {
String s = "abcdaebijkd";
ArrayList list = new ArrayList();
for(int i=0; i<s.length(); i++){
char c = s.charAt(i);
if(s.indexOf(c,i+1)>-1){
Character ch = new Character(c);
if(!list.contains(ch))
list.add(ch);
}
}
for(int i=0; i<list.size(); i++)
System.out.print(list.get(i)+",");
}
}

Answer 3

public class StringDemo {
	public static void main(String[] args) {

		String str = "abcmnabcjnabcisabckdabcfdabc";
		System.out.println(str.indexOf("abc"));// 0

		StringDemo stringDemo = new StringDemo();
		int rescult=stringDemo.searchRepeat(str, "abc");
		System.out.println(rescult);

	}

	public int searchRepeat(String string, String wantWords) {
		int repeateTime = 0;
		int startSearchPlace = 0;
		while ((startSearchPlace = string.indexOf(wantWords, startSearchPlace)) != -1) {
			repeateTime++;
			startSearchPlace += wantWords.length();
		}

		return repeateTime;
	}
}

Answer 4

import java.util.ArrayList;
public class Test {
public static void main(String[] args) {
String s = "abcdaebijkd";
ArrayList list = new ArrayList();
for(int i=0; i<s.length(); i++){
char c = s.charAt(i);
if(s.indexOf(c,i+1)>-1){
Character ch = new Character(c);
if(!list.contains(ch))
list.add(ch);
}
}
for(int i=0; i<list.size(); i++)
System.out.print(list.get(i)+",");
}
}

Answer 5

public static void main(String[] args) throws Exception {

String a = "abcdaebijkd";
String strRes = "";
for(int i=0;i<a.length();i++){
if(a.lastIndexOf(a.toCharArray()[i]) != i){
strRes = strRes + a.toCharArray()[i];
}
}
System.out.println(strRes);
}