CODEWITHSUNDEEP
java-8
Ajay Kumar
Ajay Kumar

Reputation: 3250

Filter multiple values from arrays

I have old Java Code like below:

String str1 = "aaa,bbb,ccc,ddd,eee,fff,ggg";
String str2 = "111,222,333,444,555,666,777";

//Start
String[] str1Array = str1.split(",", -1);
String[] str2Array = str2.split(",", -1);

HashMap<String, String> someMap = new HashMap<String, String>();

if (str1Array.length == str2Array.length) {
    for (int i = 0; i < str1Array.length; i++) {
        if (str1Array[i].equalsIgnoreCase("bbb") || str1Array[i].equalsIgnoreCase("ddd") || str1Array[i].equalsIgnoreCase("ggg")) {
            System.out.println("Processing:" + str1Array[i] + "-" + str2Array[i]);
            someMap.put(str1Array[i], str2Array[i]);
        }
    }
}


for (Map.Entry<String, String> entry : someMap.entrySet()) {
    System.out.println(someProcessMethod1(entry.getKey()) + " : " + someProcessMethod2(entry.getValue()));

}
//Finish

I am trying to use Java 8 (I am still learning), and trying to filter and process the filtered values. Need some pointers here.

I am starting here (I know its wrong):

String[] mixAndFilter = (String[]) Stream.concat(Stream.of(str1Array), Stream.of(str2Array)).filter(???????).thenWhatHere() 
                .toArray(b -> new String[b]);

        for (String b : mixAndFilter) {
            System.out.println(mapkey : mapValue);
        }

What should I do here to filter those three strings and use them in my someProcessMethods as its done the old way? If possible, is there a way to get thing done from Start to Finish in Java 8 way? Any pointers/solution/pseudo-code is welcome.

Update (as asked by WJS):

The goal is to:

Filter bbb, ddd, ggg strings from first array and then map those with the respective values in second array. so that the expected output is:

bbb : 222
ddd : 444
ggg : 777

Upvotes: 0

Views: 1053

Answers (1)

WJS
WJS

Reputation: 40034

The easiest way to use streams is to:

  • set up a set of strings to use as a filter list
  • first split the strings like you are doing.
  • generate a range of indices for the arrays.
  • then, if the string at the index i is contained in the set, pass that index thru the filter.
  • the use the index to populate the map
String str1 = "aaa,bbb,ccc,ddd,eee,fff,ggg";
String str2 = "111,222,333,444,555,666,777";
Set<String> filterList = Set.of("bbb", "ddd", "ggg");

String[] str1Array = str1.split(",", -1);
String[] str2Array = str2.split(",", -1);

Map<String, String> someMap = IntStream
        .range(0, str1Array.length).boxed()
        .filter(i -> filterList.contains(str1Array[i]))
        .collect(Collectors.toMap(i -> str1Array[i],
                i -> str2Array[i]));


someMap.entrySet().forEach(System.out::println);

prints

bbb=222
ddd=444
ggg=777

It is possible to make the splitting of the strings as part of the streaming process. But I found it much more cumbersome to do.

Upvotes: 2

Related Questions