java类转换异常，java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.Long

ゝ一纸荒年。 2021-09-21 16:30 480阅读 0赞

> **博客来源：**
> 
> 进行类转换的时候，Integer转换为long是出错
> 
> E/AndroidRuntime: FATAL EXCEPTION: main  
>     Process: com.example.demo, PID: 13621  
>     java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.Long  
>         at com.example.demo.MainActivity$4.onClick(MainActivity.java:76)  
>         at android.view.View.performClick(View.java:5616)  
>         at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:967)  
>         at android.view.View$PerformClick.run(View.java:22292)  
>         at android.os.Handler.handleCallback(Handler.java:751)  
>         at android.os.Handler.dispatchMessage(Handler.java:95)  
>         at android.os.Looper.loop(Looper.java:154)  
>         at android.app.ActivityThread.main(ActivityThread.java:6077)  
>         at java.lang.reflect.Method.invoke(Native Method)  
>         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)  
>         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)

我的测试代码为

Map<String,Integer> map = new HashMap<>();
    map.put("data",1);
    Integer dd = map.get("data");
    long data = map.get("data");
    Long data1 = (long) map.get("data");
    System.out.println(data);
    System.out.println(data1);
    System.out.println((data1==data));
    
    Map<String,Object> map1 = new HashMap<>();
    map1.put("data",dd);
    System.out.println(map1.get("data"));
    //正确转换的代码
    long l = Long.parseLong(map1.get("data").toString());
    //转换会报错的代码
    long l = (long)map1.get("data");
    System.out.println(l);

###  有此代码测试可见，Integer转long显示转换是可以的，当为隐式转换时就会出错 ###

### long l = Long.parseLong(map1.get("data").toString());//转换为String后再转为Long ###