java - 如何将字符串中的负值转换为 double

Question

我需要从文件(.csv)中读取值，该文件包含正值和负值。我在将字符串转换为整数时遇到错误。

    Scanner sc = new Scanner(getAssets().open("Book1.csv")).useDelimiter(",");
    int i = 0;
    while (sc.hasNext()) {
        String str  = sc.next();
        data[i] = new GraphViewData(i, Integer.parseInt(str));
        i++;
    }

下面是我的日志:

05-02 04:05:55.119: E/AndroidRuntime(3003): ' as integer
05-02 04:05:55.119: E/AndroidRuntime(3003):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
05-02 04:05:55.119: E/AndroidRuntime(3003):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
05-02 04:05:55.119: E/AndroidRuntime(3003):     at android.app.ActivityThread.access$1500(ActivityThread.java:117)
05-02 04:05:55.119: E/AndroidRuntime(3003):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
05-02 04:05:55.119: E/AndroidRuntime(3003):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-02 04:05:55.119: E/AndroidRuntime(3003):     at android.os.Looper.loop(Looper.java:123)
05-02 04:05:55.119: E/AndroidRuntime(3003):     at android.app.ActivityThread.main(ActivityThread.java:3683)
05-02 04:05:55.119: E/AndroidRuntime(3003):     at java.lang.reflect.Method.invokeNative(Native Method)
05-02 04:05:55.119: E/AndroidRuntime(3003):     at java.lang.reflect.Method.invoke(Method.java:507)
05-02 04:05:55.119: E/AndroidRuntime(3003):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
05-02 04:05:55.119: E/AndroidRuntime(3003):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
05-02 04:05:55.119: E/AndroidRuntime(3003):     at dalvik.system.NativeStart.main(Native Method)
05-02 04:05:55.119: E/AndroidRuntime(3003): Caused by: java.lang.NumberFormatException: unable to parse '893

Answer 1

要将字符串中的负值转换为 Integer，您可以使用 Integer.parseInt，如代码中所示。

我认为您看到的错误与减号无关 - 可以传递以 ASCII 减号开头的字符串(请参阅 http://docs.oracle.com/javase/1.4.2/docs/api/java/lang/Integer.html#parseInt(java.lang.String ))

顺便说一句 - 您想转换为整数还是 double ？您的问题标题提到 Double (Double.parseDouble 也接受该符号)