Java 8 : Iterating a list and adding items to new map

Question

How i can write this code in Java 8?

for (Iterator<RecordVo> iterator = list.iterator(); iterator.hasNext();) {
            RecordVo recordVo = (RecordVo) iterator.next();         
            ExecutionContext singleThreadExecutionContext = new ExecutionContext();
            singleThreadExecutionContext.put("customerId", recordVo.getCustomerId());
            singleThreadExecutionContext.put("ThreadName", "Thread-"+recordVo.getCustomerId());
            multiThreadExecutionContext.put("Partition - "+recordVo.getCustomerId(), singleThreadExecutionContext);
        }

I am learning Java8 and trying to modify my existing code to 8 lambda. Got stuck at this code snippet. I tried using stream, collect, collectors but unable to move forward — vikram singh
– vikram singh, Commented Aug 24, 2017 at 19:19
See, learning a tool means also learning where that tool is useful and where it is not. In this case, streams are not a useful tool. You'll get far more mileage by using for(each : ofList) here than from streams, and that's Java 6. — M. Prokhorov
– M. Prokhorov, Commented Aug 24, 2017 at 19:23
I was trying something like this list.forEach(recordVo->multiThreadExecutionContext.put("Partition - "+recordVo.getCustomerId(),new ExecutionContext().put("customerId", recordVo.getCustomerId()))); — vikram singh
– vikram singh, Commented Aug 24, 2017 at 19:29

Abhijit Sarkar · Accepted Answer · 2017-08-24 21:51:31Z

1

How about the following?

list.stream()
  .map(RecordVo::getCustomerId)
  .map(id -> {
    // create singleThreadExecutionContext as before
    return new SimpleImmutableEntry(id, singleThreadExecutionContext);
  })
.forEach(e -> multiThreadExecutionContext.put("Partition - " + e.getKey(), e.getValue()))

I didn't compile it, but you can do that.

answered Aug 24, 2017 at 21:51

Abhijit Sarkar

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1 Comment

vikram singh Over a year ago

It compiled and worked like a charm. Only modification i did is casting e.getValue to ExecutionContext. . (ExecutionContext)e.getValue() I am using the old way in my code but it is really helpful to know how to do it in Java 8. Thanks Abhijit.

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