Java Guava：如何结合过滤和变换？
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Guava: how to combine filter and transform?
提问by Sean Patrick Floyd
I have a collection of Strings, and I would like to convert it to a collection of strings were all empty or null Strings are removed and all others are trimmed.
我有一个字符串集合，我想将它转换为一个字符串集合，所有字符串都为空或空字符串被删除，所有其他字符串都被修剪。
I can do it in two steps:
我可以分两步完成：
final List<String> tokens =
Lists.newArrayList(" some ", null, "stuff\t", "", " \nhere");
final Collection<String> filtered =
Collections2.filter(
Collections2.transform(tokens, new Function<String, String>(){
// This is a substitute for StringUtils.stripToEmpty()
// why doesn't Guava have stuff like that?
@Override
public String apply(final String input){
return input == null ? "" : input.trim();
}
}), new Predicate<String>(){
@Override
public boolean apply(final String input){
return !Strings.isNullOrEmpty(input);
}
});
System.out.println(filtered);
// Output, as desired: [some, stuff, here]
But is there a Guava way of combining the two actions into one step?
但是有没有一种 Guava 方法可以将这两个动作合并为一个步骤？
采纳答案by Olivier Heidemann
In the upcominglatest version(12.0) of Guava, there will be a class named FluentIterable.
This class provides the missing fluent API for this kind of stuff.
在即将发布的 Guava 最新版本（12.0）中，将有一个名为FluentIterable的类。此类为此类内容提供了缺少的流畅 API。
Using FluentIterable, you should be able doing something like this:
使用 FluentIterable，你应该能够做这样的事情：
final Collection<String> filtered = FluentIterable
.from(tokens)
.transform(new Function<String, String>() {
@Override
public String apply(final String input) {
return input == null ? "" : input.trim();
}
})
.filter(new Predicate<String>() {
@Override
public boolean apply(final String input) {
return !Strings.isNullOrEmpty(input);
}
})
.toImmutableList();
