unhandled exception: java.lang.ClassNotFoundException Error

问题

I have the following Class code and when Debug it kept showing the following error:

1.) Unhandled Exception: java.lang.ClassNotfoundException 2.) Unhandled Exception:java.lang.NoSuchMethodException

Error Log:

 /apps/robotapp/Utils.java:32: error: exception IOException is never thrown in body of corresponding try statement
    } catch (IOException e) {
      ^
 /apps/robotapp/Utils.java:24: error: unreported exception ClassNotFoundException; must be caught or declared to be thrown
        final int tckName = Class.forName("libcore.io.OsConstants").getField("_SC_CLK_TCK").getInt(null);
                                         ^
/apps/robotapp/Utils.java:24: error: unreported exception NoSuchFieldException; must be caught or declared to be thrown
        final int tckName = Class.forName("libcore.io.OsConstants").getField("_SC_CLK_TCK").getInt(null);
                                                                            ^
/apps/robotapp/Utils.java:24: error: unreported exception IllegalAccessException; must be caught or declared to be thrown
        final int tckName = Class.forName("libcore.io.OsConstants").getField("_SC_CLK_TCK").getInt(null);
                                                                                                  ^
/apps/robotapp/Utils.java:25: error: unreported exception ClassNotFoundException; must be caught or declared to be thrown
        final Object os = Class.forName("libcore.io.Libcore").getField("os").get(null);
                                       ^
/apps/robotapp/Utils.java:25: error: unreported exception NoSuchFieldException; must be caught or declared to be thrown
        final Object os = Class.forName("libcore.io.Libcore").getField("os").get(null);
                                                                      ^
/apps/robotapp/Utils.java:25: error: unreported exception IllegalAccessException; must be caught or declared to be thrown
        final Object os = Class.forName("libcore.io.Libcore").getField("os").get(null);
                                                                                ^
/apps/robotapp/Utils.java:26: error: unreported exception NoSuchMethodException; must be caught or declared to be thrown
        final long tck = (Long)os.getClass().getMethod("sysconf", Integer.TYPE).invoke(os, tckName);
                                                      ^
/apps/robotapp/Utils.java:26: error: unreported exception IllegalAccessException; must be caught or declared to be thrown
        final long tck = (Long)os.getClass().getMethod("sysconf", Integer.TYPE).invoke(os, tckName);



  ^
 Note:         
 /RobotService.java uses or overrides a deprecated API.
  Note: Recompile with -Xlint:deprecation for details.
  9 errors

  FAILED

Code Snippet that Has errors:

try {
        final String[] fields = stat.substring(stat.lastIndexOf(field2End)).split(fieldSep);
        final long t = Long.parseLong(fields[fieldStartTime]);
        final int tckName = Class.forName("libcore.io.OsConstants").getField("_SC_CLK_TCK").getInt(null);
        final Object os = Class.forName("libcore.io.Libcore").getField("os").get(null);
        final long tck = (Long)os.getClass().getMethod("sysconf", Integer.TYPE).invoke(os, tckName);
        return t * msInSec / tck;
    } catch (final NumberFormatException e) {
        throw new IOException(e);
    } catch (final IndexOutOfBoundsException e) {
        throw new IOException(e);
    } catch (IOException e) {
        throw new IOException(e);
    }

回答1:

You have to add all your exceptions or use a catch all:

try {
} catch(Exception exp) { }

Your code after corrections:

try {
    final String[] fields = stat.substring(stat.lastIndexOf(field2End)).split(fieldSep);
    final long t = Long.parseLong(fields[fieldStartTime]);
    final int tckName = Class.forName("libcore.io.OsConstants").getField("_SC_CLK_TCK").getInt(null);
    final Object os = Class.forName("libcore.io.Libcore").getField("os").get(null);
    final long tck = (Long)os.getClass().getMethod("sysconf", Integer.TYPE).invoke(os, tckName);
    return t * msInSec / tck;
} catch (final NumberFormatException e) {
    throw new IOException(e);
} catch (final IndexOutOfBoundsException e) {
    throw new IOException(e);
} catch (java.lang.ClassNotfoundException e) {
    throw new IOException(e);
} catch (java.lang.NoSuchMethodException e) {
    throw new IOException(e);
} catch (IllegalAccessException e) {
    throw new IOException(e);
}

Also the IOException you were catching, is removed since it is (according to the debugger) never thrown.

回答2:

Change your code to

try {
   //do something
} catch (Exception e) {
   e.printStackTrace();
   //throw new Exception("Error occured");
}

try {
    final String[] fields = stat.substring(stat.lastIndexOf(field2End)).split(fieldSep);
    final long t = Long.parseLong(fields[fieldStartTime]);
    final int tckName = Class.forName("libcore.io.OsConstants").getField("_SC_CLK_TCK").getInt(null);
    final Object os = Class.forName("libcore.io.Libcore").getField("os").get(null);
    final long tck = (Long)os.getClass().getMethod("sysconf", Integer.TYPE).invoke(os, tckName);
    return t * msInSec / tck;
} catch (ClassNotFoundException|NoSuchFieldException|IllegalAccessException|NoSuchMethodException e) {
    throw e;
}

Much cleaner, right?

来源：https://stackoverflow.com/questions/31306932/unhandled-exception-java-lang-classnotfoundexception-error

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android

class

exception

exception-handling