java - Android 随机数 llegalArgumentException : n <= 0: 0

Question

我正在尝试生成 0 到 43 范围内的随机数。但在某些设备(OnePlus Android 5.0.2 和 Nexus 5.1)上，它抛出 java.lang.IllegalArgumentException: n <= 0: 0。我无法捕获该异常下面是我生成随机数的代码。

    Random rand = new Random();
    int maximum = mListofStrings.getMyString().size() - 1;
    Log.e("Max",""+maximum);
    Mint.logEvent("Maximum", MintLogLevel.Error);
    int randomNum;
    try{

       // randomNum = rand.nextInt(43);
        randomNum = rand.nextInt(maximum);
    }catch (IllegalArgumentException e){
        e.printStackTrace();
        randomNum = 8;
    }

    Log.e("random number", randomNum+"");

还有日志是

1   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2329)
2   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2389)
3   at android.app.ActivityThread.access$900(ActivityThread.java:147)
4   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1296)
5   at android.os.Handler.dispatchMessage(Handler.java:102)
6   at android.os.Looper.loop(Looper.java:135)
7   at android.app.ActivityThread.main(ActivityThread.java:5254)
8   at java.lang.reflect.Method.invoke(Native Method)
9   at java.lang.reflect.Method.invoke(Method.java:372)
10  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:898)
11  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693)
12Caused by: java.lang.IllegalArgumentException: n <= 0: 0
13  at java.util.Random.nextInt(Random.java:182)
14  at com.algo.toiletbreak.ShareActivity.onCreate(Unknown Source)
15  at android.app.Activity.performCreate(Activity.java:5933)
16  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
17  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2282)
18  ... 10 more

Answer 1

如果 nextInt 方法提示其参数为 0，则 maximum 为 0。这意味着 mListofStrings.getMyString().size() 返回了 1。尝试生成从 0(含)到 0(不含)的随机数是没有意义的；这样的 int 不存在。但参数值比可返回的最大随机值多一。这意味着您在分配 maximum 时不应减去 1。

int maximum = mListofStrings.getMyString().size();

您可能还想测试 size() 方法是否返回 0，并专门处理这种情况。