Java 8 - Looping Map inside List using stream

Question

I have one list and map, where i need to iterate list first and inside that loop i need to access map to form String message. I have written the same in Java 7 and it works fine. Can someone help in converting this in Java 8 streaming.

        final Map<String, String> destTabMap = ... 
        final List<String> destTabs = mappingList.get(destTabName);

        for (int j=0; j < destTabs.size(); j++) {
            String destName = destTabs.get(j);

            final String fieldValue = destTabMap.get(destName);

            if(fieldValue==null)
                continue;


           message.append(destName+"  ");
           message.append(":");
           message.append("  "+fieldValue);
           message.append("\n");
           System.out.println(destName+"  : "+fieldValue);
        }

where is mappingList definition?

Vishwa Ratna
– Vishwa Ratna

2019-04-02 05:13:53 +00:00
Commented Apr 2, 2019 at 5:13 — Vishwa Ratna
– Vishwa Ratna, Commented Apr 2, 2019 at 5:13

Ravindra Ranwala · Accepted Answer · 2019-04-02 03:07:09Z

3

You may do it like so,

String resultStr = destTabs.stream()
    .filter(s -> destTabMap.get(s) != null)
    .map(s -> s + "  :  " + destTabMap.get(s))
    .collect(Collectors.joining("\n"));

edited Apr 2, 2019 at 3:07

answered Apr 2, 2019 at 2:24

Ravindra Ranwala

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2 Comments

Naman Over a year ago

Using getOrDefault could make the mapping cleaner.

Misha Over a year ago

Consider filtering out absent keys with .filter(destTabMap::containsKey)

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