Remove duplicate values from a string in java

Question

Can anyone please let me know how to remove duplicate values from

String s="Bangalore-Chennai-NewYork-Bangalore-Chennai"; 

and output should be like

String s="Bangalore-Chennai-NewYork-";

using Java..

Any help would be appreciated.

Answer 1

This does it in one line:

public String deDup(String s) {
    return new LinkedHashSet<String>(Arrays.asList(s.split("-"))).toString().replaceAll("(^\\[|\\]$)", "").replace(", ", "-");
}

public static void main(String[] args) {
    System.out.println(deDup("Bangalore-Chennai-NewYork-Bangalore-Chennai"));
}

Output:

Bangalore-Chennai-NewYork

Notice that the order is preserved :)

Key points are:

• split("-") gives us the different values as an array
• Arrays.asList() turns the array into a List
• LinkedHashSet preserves uniqueness and insertion order - it does all the work of giving us the unique values, which are passed via the constructor
• the toString() of a List is [element1, element2, ...]
• the final replace commands remove the "punctuation" from the toString()

This solution requires the values to not contain the character sequence ", " - a reasonable requirement for such terse code.

Java 8 Update!

Of course it's 1 line:

public String deDup(String s) {
    return Arrays.stream(s.split("-")).distinct().collect(Collectors.joining("-"));
}

Regex update!

If you don't care about preserving order (ie it's OK to delete the first occurrence of a duplicate):

public String deDup(String s) {
    return s.replaceAll("(\\b\\w+\\b)-(?=.*\\b\\1\\b)", "");
}