Local variable i defined in an enclosing scope must be final or effectively final

Question

I want to implement this endpoint with internal search:

@PostMapping("terminals_risk_filter/change_order/{terminalId}")
    public ResponseEntity<?> updateFiltersPositions(@PathVariable Integer terminalId,
            @RequestBody List<ChangeOrderRiskFiltersDTO> newFiltersPositionsList) {

        List<RiskFilters> filterList = riskFilterService.findRiskFiltersByTerminalId(terminalId);

        for (int i = 0; i < newFiltersPositionsList.size(); i++) {
//          RiskFilters filter = filterList.findById(newFiltersPositionsList.get(i).getId());

            Optional<RiskFilters> filter_payload = filterList.stream().filter(f -> newFiltersPositionsList.get(i).getId() == f.getId()).findAny();
            RiskFilters filter = filter_payload.get();      

            filter.setPosition(newFiltersPositionsList.get(i).getPosition());
            riskFilterService.save(filter);
        }
        return ok().build();
    }

But I get error message Local variable i defined in an enclosing scope must be final or effectively final Can you give me some advice how I can fix this issue, please? For example can I skip the for cycle and use maybe stream into stream?

lealceldeiro · Accepted Answer · 2019-06-13T16:30:49.673

Can you give me some advice how I can fix this issue, please?

Why does this happen? You can read about it here: Lambdas: local variables need final, instance variables don't

Minimal changes to solve your problem: Don't use the i variable itself. Create a copy of it and make it final.

final int iCopy = i;
Optional<RiskFilters> filter_payload = filterList.stream().filter(f -> newFiltersPositionsList.get(iCopy).getId() == f.getId()).findAny();

For example can I skip the for cycle and use maybe stream into stream?

You could give it a try:

// replace the for-loop

// or just.... `newFiltersPositionsList.forEach(/* ... */)`
newFiltersPositionsList.stream().forEach(filterPosition -> {
    Optional<RiskFilters> filter_payload = filterList.stream()
            .filter(f -> filterPosition.getId() == f.getId())
            .findAny();
    RiskFilters filter = filter_payload.get();

    filter.setPosition(filterPosition.getPosition());
    riskFilterService.save(filter);
});

Also, you could use a for-each instead of a for-loop:

for (ChangeOrderRiskFiltersDTO filterPosition : newFiltersPositionsList) {
    Optional<RiskFilters> filter_payload = filterList.stream()
           .filter(f -> filterPosition.getId() == f.getId())
           .findAny();
    RiskFilters filter = filter_payload.get();
    filter.setPosition(filterPosition.getPosition());
    riskFilterService.save(filter);
}

@PeterPenzov I added an alternative to your for-loop. There can be many other good combinations to solve this. — lealceldeiro, Jun 13 '19 at 15:21

score 2 · Answer 2 · answered Jun 13 '19 at 15:18

You can do it like below as well.

final ChangeOrderRiskFiltersDTO dto = newFiltersPositionsList.get(i);
Optional<RiskFilters> filter_payload = filterList.stream().filter(f -> dto.getId() == f.getId()).findAny();
if(filter_payload.isPresent()){
  RiskFilters filter = filter_payload.get();
  //More operations
}

score 2 · Answer 3 · answered Jun 13 '19 at 15:20

2

If you want to avoid the simple solution of adding a final copy of the i, you can extract the actual "final" information:

final int id = newFiltersPositionsList.get(i).getId()

And your lambda can become:

f -> id == f.getId()

answered Jun 13 '19 at 15:20

MaanooAk

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score 0 · Answer 4 · answered Oct 27 '21 at 08:37

This is not an answer to the original question.

The same error message appears if you try to assign a variable in an enclosing class from an inner anonymous class. For example:

    int result = 0;
    hibernateSession.doWork(new Work() {
        @Override
        public void execute(Connection conn) throws SQLException {
            result = 1;
        }
    });

In this case, I found a workaround pointing to an array:

    int[] result = new int[1];
    hibernateSession.doWork(new Work() {
        @Override
        public void execute(Connection conn) throws SQLException {
            result[0] = 1;
        }
    });

Local variable i defined in an enclosing scope must be final or effectively final

4 Answers4