线程优化插件，会在android5.1及以下版本报错。

[CodeIdeal]

reproduce repo: https://github.com/CodeIdeal/booster_adnroid_5_incompatible_example

• System version Android 5.1.1
• Java version JDK 11
• Gradle version 6.7.1
• Android Gradle plugin version 4.1.3
• Booster version 4.10.0
• Stack traces

  FATAL EXCEPTION: main
  Process: tech.cabana.toys, PID: 11857 
  java.lang.RuntimeException: Unable to start activity ComponentInfo{tech.cabana.toys/tech.cabana.toys.MainActivity}: java.lang.IllegalArgumentException: Core threads must have nonzero keep alive times 
  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2587)
  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2659)
  at android.app.ActivityThread.access$1000(ActivityThread.java:169)
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1467)
  at android.os.Handler.dispatchMessage(Handler.java:102)
  at android.os.Looper.loop(Looper.java:159)
  at android.app.ActivityThread.main(ActivityThread.java:5671)
  at java.lang.reflect.Method.invoke(Native Method)
  at java.lang.reflect.Method.invoke(Method.java:372)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:964)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:759)
  Caused by: java.lang.IllegalArgumentException: Core threads must have nonzero keep alive times
  at java.util.concurrent.ThreadPoolExecutor.allowCoreThreadTimeOut(ThreadPoolExecutor.java:1639)
  at com.didiglobal.booster.instrument.ShadowScheduledThreadPoolExecutor.<init>(ShadowScheduledThreadPoolExecutor.java:43)
  at tech.cabana.toys.MainActivity.onCreate(MainActivity.kt:16)
  at android.app.Activity.performCreate(Activity.java:6162)
  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2508)
  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2659)
  at android.app.ActivityThread.access$1000(ActivityThread.java:169)
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1467)
  at android.os.Handler.dispatchMessage(Handler.java:102)
  at android.os.Looper.loop(Looper.java:159)
  at android.app.ActivityThread.main(ActivityThread.java:5671)
  at java.lang.reflect.Method.invoke(Native Method)
  at java.lang.reflect.Method.invoke(Method.java:372)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:964)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:759)

大致看了下，好像是因为在android5.1以下时，默认的keepAliveTime为0. 在低版本中使用线程优化插件回因为主动调用allowCoreThreadTimeOut,从而导致在校验keepAliveTime值的时候抛出IllegalArgumentException。

    public void allowCoreThreadTimeOut(boolean value) {
        if (value && keepAliveTime <= 0)
            throw new IllegalArgumentException("Core threads must have nonzero keep alive times");
        if (value != allowCoreThreadTimeOut) {
            allowCoreThreadTimeOut = value;
            if (value)
                interruptIdleWorkers();
        }
    }

这个问题应该可以在ShadowScheduledThreadPoolExecutor中直接指定默认的keepAliveTime值解决。

[CodeIdeal]

359 目前已提了PR，如果没问题麻烦合并下。 @johnsonlee