用 ifPresent 和 orElse 替换 isPresent

huangapple
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英文:

Replacing isPresent with ifPresent and orElse

问题

  1. AtomicReference<Employee> employeeValue = null;
  2. questions.forEach(question -> {
  3.     employeeValue = question.isBoolean().isPresent()
  4.         ? new AtomicReference<>(Employee.builder()
  5.                 .withBooleanValue(Boolean.valueOf(question.value()))
  6.                 .build())
  7.         : new AtomicReference<>(Employee.builder()
  8.                 .withStringValue(question.value())
  9.                 .build());
  11.     Record record = Record.builder()
  12.             .withId(question.id())
  13.             .withValue(employeeValue.get())
  14.             .build();
  15.     answers.add(record);
  16. });

如果我使用 ifPresent 和 orElse 分别与匿名内部函数分开使用，应该如何操作？

希望能对您有所帮助。

英文:

I have the following logic in my method where I check for the value of an optional parameter, and depending on that I build another object.

  1. AtomicReference&lt;Employee&gt; employeeValue = null;
  2.     questions.forEach(question -&gt; {
  3.         if(question.isBoolean().isPresent()) {
  4.             employeeValue.set(Employee.builder()
  5.                     .withBooleanValue(Boolean.valueOf(question.value()))
  6.                     .build());
  7.         } else {
  8.             employeeValue.set(Employee.builder()
  9.                     .withStringValue(question.value())
  10.                     .build());
  11.         }
  12.         Record record = Record.builder()
  13.                 .withId(question.id())
  14.                 .withValue(employeeValue.get())
  15.                 .build();
  16.         answers.add(record);
  17.     });

How can I replace the above with ifPresent and orElse? I'm using Java 8 and therefore ifPresentOrElse method is not available. If I am to use ifPresent and orElse separately with anonymous inner function, how do I go about it?

Any help would be much appreciated.

答案1

得分: 2

你既不需要 isPresent() 也不需要 ifPresent()。你不需要 peek()（如其他答案中所示），也不需要 AtomicReference（如问题中所示）。我相信这样做可以：

  1. questions.forEach(question -> {
  2.     Employee empl = question.isBoolean()
  3.             .map(b -> Employee.builder()
  4.                     .withBooleanValue(Boolean.valueOf(question.value()))
  5.                     .build())
  6.             .orElseGet(() -> Employee.builder()
  7.                     .withStringValue(question.value())
  8.                     .build());
  9.     Record record = Record.builder()
  10.             .withId(question.id())
  11.             .withValue(empl)
  12.             .build();
  13.     answers.add(record);
  14. });

如果你愿意，你可能可以将这个思想应用到其他答案中的流内部。与使用 Stream.forEach() 不同，我更喜欢收集到一个集合中，比如一个列表，然后使用 answers.addAll()。

英文:

You neither need isPresent() nor ifPresent(). You don’t need peek() (as in the other answer) nor an AtomicReference (as in the question). I believe that this does it:

  1. 	questions.forEach(question -&gt; {
  2. 		Employee empl = question.isBoolean()
  3. 				.map(b -&gt; Employee.builder()
  4. 	                    .withBooleanValue(Boolean.valueOf(question.value()))
  5. 	                    .build())
  6. 				.orElseGet(() -&gt; Employee.builder()
  7. 	                    .withStringValue(question.value())
  8. 	                    .build());
  9. 		Record record = Record.builder()
  10. 				.withId(question.id())
  11. 				.withValue(empl)
  12. 				.build();
  13. 		answers.add(record);
  14. 	});

You can probably apply this idea inside the stream from the other answer if you want. Rather than using Stream.forEach() I’d prefer to collect into a collection like a list and then use answers.addAll().

答案2

得分: 1

你可以通过流式处理questions，并使用peek和map-orElse结构来实现相同的结果：

  1. questions.stream()
  2.     .peek(question -> {
  3.         Employee employee = question.isBoolean()
  4.             .map(b -> Employee.builder().withBooleanValue(Boolean.valueOf(question.value())).build())
  5.             .orElse(Employee.builder().withStringValue(question.value()).build());
  6.         employeeValue.set(employee);
  7.     })
  8.     .map(question -> Record.builder().withId(question.id()).withValue(employeeValue.get()).build())
  9.     .forEach(answers.add(answer)); // 你是不是指的是'record'?

但说实话，这并没有改变太多 - 你的实现可能看起来不太像“Java八”的风格，但是已经很好了 用 ifPresent 和 orElse 替换 isPresent

英文:

You can stream through questions and use peek and map-orElse construction to achieve the same result:

  1. questions.stream()
  2.     .peek(question -&gt; {
  3.             Employee employee = question.isBoolean()
  4.                 .map(b -&gt; Employee.builder().withBooleanValue(Boolean.valueOf(question.value())).build())
  5.                 .orElse(Employee.builder().withStringValue(question.value()).build());
  6.             employeeValue.set(employee);
  7.         }
  8.     )
  9.     .map(question -&gt; Record.builder().withId(question.id()).withValue(employeeValue.get()).build())
  10.     .forEach(answers.add(answer)); // did you mean &#39;record&#39;?

But to be honest it does not change a lot - your implementation looks maybe less "java eightish" but is fine 用 ifPresent 和 orElse 替换 isPresent

huangapple
  • 本文由 发表于 2020年9月9日 07:40:27
  • 转载请务必保留本文链接：https://go.coder-hub.com/63802894.html
  • if-statement
  • java
  • lambda
  • option-type
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