java.lang.ClassCastException : java. lang.String 无法转换为 java.lang.Long

Question

我创建了这个简单的示例，用于读取 Linux 正常运行时间:

public String getMachineUptime() throws IOException {
    String[] dic = readData().split(" ");

    long s = (long) Array.get(dic, 1);
    return calculateTime(s);
}

private String readData() throws IOException {
    byte[] fileBytes;
    File myFile = new File("/proc/uptime");
    if (myFile.exists()) {
        try {
            fileBytes = Files.readAllBytes(myFile.toPath());
        } catch (java.nio.file.AccessDeniedException e) {
            return null;
        }

        if (fileBytes.length > 0) {
            return new String(fileBytes);
        }
    }
    return null;
}

private String calculateTime(long seconds) {
    int day = (int) TimeUnit.SECONDS.toDays(seconds);
    long hours = TimeUnit.SECONDS.toHours(seconds)
            - TimeUnit.DAYS.toHours(day);
    long minute = TimeUnit.SECONDS.toMinutes(seconds)
            - TimeUnit.DAYS.toMinutes(day)
            - TimeUnit.HOURS.toMinutes(hours);
    long second = TimeUnit.SECONDS.toSeconds(seconds)
            - TimeUnit.DAYS.toSeconds(day)
            - TimeUnit.HOURS.toSeconds(hours)
            - TimeUnit.MINUTES.toSeconds(minute);

    return "Day " + day + " Hour " + hours + " Minute " + minute
            + " Seconds " + second;
}

当我运行代码时，我收到此异常:

java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Long

还有其他方法可以转换结果吗？

Answer 1

我相信你必须更换

long s = (long) Array.get(dic, 1);

与

long s = Long.valueOf((String) Array.get(dic, 1));

或者更好:

long s = Long.valueOf(dic[1]);

原因是您的数组由 String 对象组成，并且直接转换不起作用。