Question

我正在尝试从0到43范围生成随机数。但在Some Devices（OnePlus Android 5.0.2和Nexus 5.1）中，它抛出java.lang.IllegalArgumentException：n＆lt; = 0：0。我无法捕获该异常以下是我的代码生成随机数。< / p>

    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Log

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方法抱怨其参数为0，则maximum为0。这意味着mListofStrings.getMyString().size()返回1。尝试从0包含0独占生成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个。这意味着您在分配1时不应减去maximum。

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

您可能还想测试size()方法是否返回0，并专门处理该案例。

Answer 2

public static int randInt(int min, int max) 
{
    Random rand = new Random();
    return rand.nextInt((max - min) + 1) + min;
}

将min传递为0，最大值为43（如您所述）并获取范围内的随机数。

Android随机数llegalArgumentException：n＆lt; = 0：0

2 个答案: