Create a new string that will consist of common letters from other two strings in java

Question

public class StringEx {

public static void main(String[] args){

    String s1 ="abcc";
    String s2 = "cbaa";

    getCommon(s1,s2);
}

private static void getCommon(String s1, String s2) {
    char[] c1 = s1.toCharArray();
    char[] c2 = s2.toCharArray();

    char[] commonAry = new char[10];

    for(int i=0;i < (c1.length)-1;i++){
    for(int j=0;j<(c2.length)-1;j++){

        if(c1[i]==c2[j]){
            int k=0;
            commonAry[k]=c1[i];
            k++; 
        }
    }
    }

    System.out.println(commonAry);

}

}

the above program is giving an output like "c n some square boxer after that".. what is wrong in above code.

What do you expect `System.out.println(commonAry);` to do? And why? — Sotirios Delimanolis, Feb 01 '14 at 06:03
length of `commonAry` should be = `min(c1.length, c2.length)`. your teacher will cut marks for `char[10]` — Grijesh Chauhan, Feb 01 '14 at 06:04
Once you've answered my question above, read [this](http://stackoverflow.com/questions/409784/simplest-way-to-print-an-array-in-java). — Sotirios Delimanolis, Feb 01 '14 at 06:05
put letters of one word in a Set, then iterate over another word and check presence of each letter. — Alexei Kaigorodov, Feb 01 '14 at 06:24
@SaurabhSharma `what is wrong in above code.` is the question. — Michael Yaworski, Feb 01 '14 at 06:57
@mikeyaworski Thanks. I can see that. What is expected was my question. — Saurabh Sharma, Feb 01 '14 at 07:02
@SaurabhSharma I was being sarcastic. Either way, how can you not know what he's expecting? `common letters from other two strings` sounds pretty self-explanatory. He's probably expecting `abc` — Michael Yaworski, Feb 01 '14 at 07:17

Nambi · Answer 1 · 2014-02-01T15:20:32.953

4

Use Set<character> retainAll() method to get the intersect between the two String

public static void getCommon(String s1,String s2){


         char[] s1Array = s1.toCharArray();  
         char [] s2Array = s2.toCharArray();  


     Set<Character>s1CharSet = new HashSet<Character>();  
     Set<Character>s2CharSet = new HashSet<Character>();  

     for(char c:s1Array){  
         s1CharSet.add(c);  
     }  

     for(char c: s2Array){  
         s2CharSet.add(c);  
     }  

     s1CharSet.retainAll(s2CharSet);  

     if(s1CharSet.size()==0){  
        System.out.println("There are no common characters between the two strings");  
     }  

     else{  
         System.out.println(s1CharSet);  
     }  


     }

output

  [b, c, a]

Demo

edited Feb 01 '14 at 15:20

answered Feb 01 '14 at 06:29

Nambi

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Did you actually run this, and get `"abc"` as the output? – Dawood ibn Kareem Feb 01 '14 at 08:43
@DavidWallace Yes I get the abc as the output and add the Demo link check it out – Nambi Feb 01 '14 at 09:59
OK. You do realise that with different input strings, this isn't going to work out quite as nicely, right? There are at least three bugs, which coincidentally fail to manifest, with this particular input. – Dawood ibn Kareem Feb 01 '14 at 10:14
@DavidWallace Thanks, i have found the difficults when I tried by using == comparator ,so i tried it retainAll method in set, can you plz check my edited answer.. – Nambi Feb 01 '14 at 15:25
1

It looks much, much better now; and as far as I can see, it works correctly. Note that you don't need to iterate through the `char` arrays yourself, to make the sets. You can just write `Set s1CharSet = new HashSet(Arrays.asList(s1Array));` – Dawood ibn Kareem Feb 01 '14 at 17:09

score 2 · Answer 2 · edited May 23 '17 at 12:17

firstly, you are not looping over all the char array, your looping should be:

for(int i=0;i < (c1.length);i++)

secondly, you must initialize the index k out of your loops, thirdly, this operation is not commutative, that means

getCommon(String s1, String s2)

and

getCommon(String s2, String s1)

won't give the same results,

and finally, because you're trying to get common letters, so why not break the inner loop just after finding any similar character in the other array?

Note: you should omit any redundancy in your first string, or in the result, after calculation.
and for square letters, I refer you to this post https://stackoverflow.com/a/13505323/1951298

Create a new string that will consist of common letters from other two strings in java

2 Answers2