用 Java-8 Streams 替换“for”循环中的 if-else
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/31609716/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Replacing if-else within 'for' loops with Java-8 Streams
提问by sidgate
I have following simple code that I am trying to convert to functional style
我有以下简单的代码，我正在尝试将其转换为功能样式
for(String str: list){
if(someCondition(str)){
list2.add(doSomeThing(str));
}
else{
list2.add(doSomethingElse(str));
}
}
Is it easily possible to replace this loop with stream? Only option I see is to iterate over the stream twice with two different filter conditions.
是否可以轻松地用流替换此循环？我看到的唯一选择是使用两种不同的过滤条件对流进行两次迭代。
采纳答案by Jon Skeet
It sounds like you can just use mapwith a condition:
听起来你可以只使用map一个条件：
List<String> list2 = list
.stream()
.map(str -> someCondition(str) ? doSomething(str) : doSomethingElse(str))
.collect(Collectors.toList());
Short but complete example mapping short strings to lower case and long ones to upper case:
简短但完整的示例将短字符串映射到小写，将长字符串映射到大写：
import java.util.*;
import java.util.stream.*;
public class Test {
public static void main(String[] args) {
List<String> list = Arrays.asList("abC", "Long Mixed", "SHORT");
List<String> list2 = list
.stream()
.map(str -> str.length() > 5 ? str.toUpperCase() : str.toLowerCase())
.collect(Collectors.toList());
for (String result : list2) {
System.out.println(result); // abc, LONG MIXED, short
}
}
}
