未处理的异常：java.lang.ClassNotFoundException 错误答案

【问题标题】：unhandled exception: java.lang.ClassNotFoundException Error未处理的异常：java.lang.ClassNotFoundException 错误
【发布时间】：2015-07-09 02:07:48
【问题描述】：

我有以下类代码，在调试时它一直显示以下错误：

1.) 未处理的异常：java.lang.ClassNotfoundException 2.) 未处理异常：java.lang.NoSuchMethodException

错误日志：

 /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

有错误的代码片段：

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);
    }

【问题讨论】：

您的代码似乎丢失了一半（没有可见的 catch 块）。
@MattClark 是的，我知道。我在问如何纠正它

标签： android class exception exception-handling

【解决方案1】：

您必须添加所有异常或使用全部捕获：

try {
} catch(Exception exp) { }

更正后的代码：

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);
}

您捕获的 IOException 也被删除，因为它（根据调试器）从未被抛出。

【讨论】：

或者替代方案： public void functionName() throws Exception { } 那么你不必在那里捕获它们。他们将不得不被抓到某个地方，因为他们只是被委派给调用函数。

【解决方案2】：

将您的代码更改为

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

或

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;
}

干净多了，对吧？

【讨论】：