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

Aug 16, 2024#java33

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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 code worked perfectly.

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. During debugging, I found that the entire peek() operation was not executed and 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 used the map() operation to return JSONObject, and then used the terminal operation toList() to finish perfectly!!!