如何从字符串中提取短语

Question

我如何将两个“16”拉出来

• Bar Foo Bar: Foo8:16 Foo Bar Bar foo barz
• 8:16 Foo Bar Bar foo barz

这是我尝试过的

String V,Line ="Bar Foo Bar: Foo8:16 Foo Bar Bar foo barz";
V = Line.substring(Line.indexOf("([0-9]+:[0-9]+)+")+1);
V = V.substring(V.indexOf(":")+1, V.indexOf(" "));
System.out.println(V);

这是我得到的错误

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -9
    at java.lang.String.substring(String.java:1955)  
    at Indexing.Index(Indexing.java:94)  
    at Indexing.main(Indexing.java:24)

我在http://regexr.com/ 测试了 regex("([0-9]+:[0-9]+)+") 并正确突出显示“8:16”

Answer 1

您需要将捕获组放在第二个[0-9]+（或等效的\d+）上并使用Matcher#find()：

String value1 = "Bar Foo Bar: Foo8:16 Foo Bar Bar foo barz";
String pattern1 = "\\d+:(\\d+)"; // <= The first group is the \d+ in round brackets
Pattern ptrn = Pattern.compile(pattern1);
Matcher matcher = ptrn.matcher(value1);
if (matcher.find())
    System.out.println(matcher.group(1)); // <= Print the value captured by the first group
else
    System.out.println("false");

见demo

Answer 2

String.indexOf(String str) 不采用正则表达式。它需要一个字符串。

你可以这样做：

String V, Line = "Bar Foo Bar: Foo8:16 Foo Bar Bar foo barz";
V = Line.substring(Line.indexOf("16"), Line.indexOf("16") + 2);
System.out.println(V);

或者为了看起来更整洁，你可以替换这一行：

V = Line.substring(Line.indexOf("16"), Line.indexOf("16") + 2);

与：

int index = Line.indexOf("16");
V = Line.substring(index, index + 2);