Question

我想通过在Scala中使用正则表达式从字符串中提取子字符串。

例如，字符串

line = "[129]: (29) -> (1): Rumor"

我想从行中提取三个数字和最后一个子字符串（"Rumor"）。

如何在scala中实现它？

更新

谢谢@Shyamendra Solanki，它现在有效。但我有另一个问题。当我从文件中读取一行并使用正则表达式解析此行时，eclipse报告奇怪的错误（我不知道什么是错的）。但如果我不使用它，则不会报告错误。

val pattern = """\[(\d+)\]:\s\((\d+)\)\s\W\W\s\((\d)\):\s(\w+)""".r // define regex
for(line: String <- Source.fromFile(f1).getLines()){
    val pattern(clock, from, to, msg) = line
    println(clock+", "+ from+", "+to+", msg")
}

错误：

Exception in thread "AWT-EventQueue-0" scala.MatchError: [1]: (1) <- (0): Init([LNode;@1f18e146,Full@1a6dca9d) (of class java.lang.String)
    at TwoNodeQuery$$anon$1$$anonfun$1$$anonfun$apply$mcV$sp$2.apply(Analysis.scala:74)
    at TwoNodeQuery$$anon$1$$anonfun$1$$anonfun$apply$mcV$sp$2.apply(Analysis.scala:73)
    at scala.collection.Iterator$class.foreach(Iterator.scala:727)
    at scala.collection.AbstractIterator.foreach(Iterator.scala:1157)
    at TwoNodeQuery$$anon$1$$anonfun$1.apply$mcV$sp(Analysis.scala:73)
    at scala.swing.Action$$anon$2.apply(Action.scala:60)
    at scala.swing.Action$$anon$1.actionPerformed(Action.scala:78)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6505)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3312)
    at java.awt.Component.processEvent(Component.java:6270)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
    at java.awt.EventQueue.access$200(EventQueue.java:103)
    at java.awt.EventQueue$3.run(EventQueue.java:694)
    at java.awt.EventQueue$3.run(EventQueue.java:692)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:708)
    at java.awt.EventQueue$4.run(EventQueue.java:706)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

Answer 1

val re = """\[(\d+)\]:\s\((\d+)\)\s\W\W\s\((\d)\):\s(\S+)""".r // define regex 
val s = "[129]: (29) -> (1): Rumor"   // line to match
val re(n1, n2, n3, s1) = s            // pattern match and extract values
(n1.toInt, n2.toInt, n3.toInt, s1)    // convert to expected types

Answer 2

从Scala 2.13开始，可以按unapplying a string interpolator模式匹配String s：

val s"[$n1]: ($n2) -> ($n3): $rumor" = "[129]: (29) -> (1): Rumor"
n1: String = 129
n2: String = 29
n3: String = 1
rumor: String = Rumor

请注意，我们也可以在提取器内的{em> 中使用regex。

因此，为了强制前三个数字为有效整数：

val Nbr = "(\\d+)".r

"[129]: (29) -> (1): Rumor" match {
  case s"[${Nbr(n1)}]: (${Nbr(n2)}) -> (${Nbr(n3)}): $rumor" =>
    Some(n1.toInt, n2.toInt, n3.toInt, rumor)
  case _ => None
}
// Option[(Int, Int, Int, String)] = Some((129,29,1,Rumor))

如何在scala中提取匹配的字符串？

2 个答案: