Question

如果找不到匹配项，我的应用会突然停止。这是一段代码：

while (matcher.find()) {

  tagValues.add(matcher.group(1));


 }

如何向用户显示没有匹配且仍然在同一页面上？这是logcat。它给出了IndexOutOfBounds异常。

java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
04-16 21:17:56.700: E/AndroidRuntime(19492):    at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:255)
04-16 21:17:56.700: E/AndroidRuntime(19492):    at java.util.ArrayList.get(ArrayList.java:308)
04-16 21:17:56.700: E/AndroidRuntime(19492):    at com.approve.smsapp.Conversation$1.onItemClick(Conversation.java:115)
04-16 21:17:56.700: E/AndroidRuntime(19492):    at android.widget.AdapterView.performItemClick(AdapterView.java:299)
04-16 21:17:56.700: E/AndroidRuntime(19492):    at android.widget.AbsListView.performItemClick(AbsListView.java:1113)
04-16 21:17:56.700: E/AndroidRuntime(19492):    at android.widget.AbsListView$PerformClick.run(AbsListView.java:2904)
04-16 21:17:56.700: E/AndroidRuntime(19492):    at android.widget.AbsListView$3.run(AbsListView.java:3638)

Answer 1

请添加更多代码以更好地了解您的问题。看下面一个简单的匹配器示例，可能会对您有所帮助：

public class RegexTestPatternMatcher {
  public static final String EXAMPLE_TEST = "This is my small example string which I'm going to use for pattern matching.";

  public static void main(String[] args) {
    Pattern pattern = Pattern.compile("\\w+");
    // in case you would like to ignore case sensitivity,
    // you could use this statement:
    // Pattern pattern = Pattern.compile("\\s+", Pattern.CASE_INSENSITIVE);
    Matcher matcher = pattern.matcher(EXAMPLE_TEST);
    // check all occurance
    while (matcher.find()) {
      System.out.print("Start index: " + matcher.start());
      System.out.print(" End index: " + matcher.end() + " ");
      System.out.println(matcher.group());
    }
    // now create a new pattern and matcher to replace whitespace with tabs
    Pattern replace = Pattern.compile("\\s+");
    Matcher matcher2 = replace.matcher(EXAMPLE_TEST);
    System.out.println(matcher2.replaceAll("\t"));
  }
}

Answer 2

您正在执行matcher.group(1)，但您的正则表达式并未捕获第一组。因此，要么将group(1)更改为group(0)，要么捕获相应的组。

以下是引发java.lang.IndexOutOfBoundsException例外的示例。

String input = "some input";
Pattern pattern = Pattern.compile(".+");
Matcher m = pattern.matcher(input);
while (m.find()) {
    System.out.println(m.group(1));
}

以上案例的解决方案是，

在正则表达式中使用组捕获：

Pattern pattern = Pattern.compile("(.+)");
                                   ^  ^  group capture added.

或使用适当的组，例如在这种情况下使用group(0)

System.out.println(m.group(0));

如何在使用matcher.find（）时解决IndexOutOfBounds异常？

2 个答案: