Comparing values in two strings

Question

I'm trying to compare two strings with one another. One contains for example :

String x =" aa bb cc dd ee " 

and the other one :

String y =" aa bb "

Now I want to do this

if (any values from String x EXISTS IN String y) 
if (y.matches(???)){System.out.println("true");}
else{System.out.println("false");}

I know that I can to do the opposite by using regex, like this :

if (x.matches(".*"+y+".*")){do something}

But I'd like to know if there is any way to check if any value in String x matches String y.

• Makoto: Should your code return true if x = "aa bb cc dd ee" and y = ee aa?

Answer 1

Assuming that what you call "a value in a String" is a pair of characters between spaces, split both Strings to transform them in sets of values (Set<String>), and use the Set methods to compute what you want (containsAll(), removeAll(), retainAll(), etc.).

• Loop Masters: No, that was just an example I'm reading data from a file and it can't simply split
• JB Nizet: Then explain what you call a "value". But I don't see how you could not constitute a set of words from a file.
• JB Nizet: I'm still thinking that you should just have two sets, and compare those sets. The only difference is that you should use Date to represent a Date, and not String. BTW, you just accepted an answer that does exactly what I suggest to do in my answer (but in a suboptimal way).

Answer 2

If you are trying to see if String x is in String y somewhere then use the .contains(String str) method.

If you are trying to determine if the white space delimited parts of the strings are contained within y then you will need to split and then do contains on each part of the split operation.

• Loop Masters: .contain doesn't work because there are values in sting x that do not exist in the other one.
• Jon Taylor: That would be why I suggested splitting x into whitespace delimited parts and then using contains on each of those parts. Much as JB Nizet suggested in an answer below.

Answer 3

String x_trimmed = x.trim();
String y_trimmed = y.trim();
String[] x_elements = x_trimmed.split("\\s+");
String[] y_elements = y_trimmed.split("\\s+");
Set<String> x_elementsSet = new HashSet<String>(Arrays.asList(x_elements));
Set<String> y_elementsSet = new HashSet<String>(Arrays.asList(y_elements));
for (String x : x_elementsSet) {
 if (y_elementsSet.contains(x)) {
 System.out.println("true");
 } else {
 System.out.println("false");
 }
}

• JB Nizet: Why not use String.trim() to trim? Why use List instead of Set? Why transform the array to a List at each iteration?
• user278064: @JBNizet: Right! Thanks a lot for the hint! :)
• JB Nizet: Just because you name a variable xxxSet doesn't make it a Set. Use java.util.HashSet instead of a java.util.List. It's much more efficient at lookups (O(1) rather than O(n)).