Java 等效于 C#'s ' Enumerable.Any'

Question

在 C# 中，有一种方法可以减少 if 语句的长度，方法是使用 Enumerable.Any 检查序列中的元素是否满足条件 (https://msdn.microsoft.com/en-us/library/vstudio/bb534972%28v=vs.100%29.aspx)。

例如代替:

If ( string.Contains(">") || string.Contains("<") || string.Contains("&") || string.Contains("l") || string.Contains("p") )

我们可以使用

if (new [] { ">", "<", "&", "l", "p"}.Any(w => string.Contains(w)))

在 Java 中是否有等效的(如果不是更好的话)方法？

Answer 1

使用 Java 8，您可以编写如下代码:

if (Stream.of(">", "<", "&", "l", "p").anyMatch(string::contains)) {
  ...
}

出于好奇，我运行了一个基准来比较这种方法和正则表达式。下面的代码和结果(分数越低 = 越快)。流的性能比正则表达式好一个数量级。

Benchmark                                    (s)  Mode  Samples     Score    Error  Units
c.a.p.SO30940682.stream   >aaaaaaaaaaaaaaaaaaaaa  avgt       10    49.942 ±  1.936  ns/op
c.a.p.SO30940682.stream   aaaaaaaaaaaaaaaaaaaaa>  avgt       10    54.263 ±  1.927  ns/op
c.a.p.SO30940682.stream   aaaaaaaaaaaaaaaaaaaaap  avgt       10   131.537 ±  4.908  ns/op
c.a.p.SO30940682.stream   paaaaaaaaaaaaaaaaaaaaa  avgt       10   129.528 ±  7.352  ns/op
c.a.p.SO30940682.regex    >aaaaaaaaaaaaaaaaaaaaa  avgt       10   649.867 ± 27.142  ns/op
c.a.p.SO30940682.regex    aaaaaaaaaaaaaaaaaaaaa>  avgt       10  1047.122 ± 89.230  ns/op
c.a.p.SO30940682.regex    aaaaaaaaaaaaaaaaaaaaap  avgt       10  1029.710 ± 61.055  ns/op
c.a.p.SO30940682.regex    paaaaaaaaaaaaaaaaaaaaa  avgt       10   694.309 ± 32.675  ns/op

代码:

@State(Scope.Benchmark)
@BenchmarkMode(Mode.AverageTime)
public class SO30940682 {

  @Param({">aaaaaaaaaaaaaaaaaaaaa", "aaaaaaaaaaaaaaaaaaaaa>",
          "aaaaaaaaaaaaaaaaaaaaap", "paaaaaaaaaaaaaaaaaaaaa"}) String s;

  @Benchmark public boolean stream() {
    return Stream.of(">", "<", "&", "l", "p").anyMatch(s::contains);
  }

  @Benchmark public boolean regex() {
    return s.matches("^.*?(>|<|&|l|p).*$");
  }
}