If a Stream does not have a terminal operation, it will ...

Aug 16, 2024#java259

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If a Stream does not have a terminal operation, the intermediate operations will not be executed. In the code written today, the peek() operation was skipped, resulting in an empty list. After modifying the code to use map() operation to return JSONObject and adding a terminal operation toList(), the issue was resolved.

If a Stream does not have a terminal operation, the intermediate operations of this stream will not be executed

This is the code I wrote today, I found that there was no data in the list at the end, so I debugged it, and during debugging I found: the entire peek() operation was not executed, it was skipped directly

List<JSONObject> list = new ArrayList<>();
sbdqas.queryAll(qs).stream()
        .peek(AbstractStandingBookData -> {
            Map<String, String> contentMap = AbstractStandingBookData.toContentMap();
            contentMap.put("totalReceivables", AmountUtil.convertAmountSmallFormat(contentMap.get("totalReceivables")));
            contentMap.put("totalPayable", AmountUtil.convertAmountSmallFormat(contentMap.get("totalPayable")));
            list.add(new JSONObject(contentMap));
        });

Later, I refactored the code, directly returning JSONObject in the map() operation, and the terminal operation toList() worked perfectly!!!