#714 NoSuchMethodError after applying ProGuard

[John Bailey]

NoSuchMethodError after applying ProGuard
Following occurs with android studio 3.1.3 with Proguard 5.3.3,m not sure why java classes get obfuscated,

java.lang.NoSuchMethodError: No virtual method a(Ljava/lang/Object;)Ljava/lang/StringBuilder; in class Ljava/lang/StringBuilder; or its super classes (declaration of 'java.lang.StringBuilder' appears in /system/framework/core-oj.jar)
        at com.myapplication.MainApplication.<init>(SourceFile:81)
        at java.lang.Class.newInstance(Native Method)
        at android.app.Instrumentation.newApplication(Instrumentation.java:1102)
        at android.app.Instrumentation.newApplication(Instrumentation.java:1087)
        at android.app.LoadedApk.makeApplication(LoadedApk.java:983)
        at android.app.ActivityThread.handleBindApplication(ActivityThread.java:5715)
        at android.app.ActivityThread.-wrap1(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1656)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

[John Bailey]

above occurs while acessing
public String DEFAULT_APP_FOLDER_MAIN = Environment
.getExternalStorageDirectory() + "/MyRecordings/";

[Eric Lafortune]

It seems like the input contains rt.jar or android.jar, so they get obfuscated along with your own code. Do your configuration files don't contain any -injars settings? The Android build system already sets those for you.

Alternatively, your compiled code accidentally contains a copy of StringBuilder. You should then try a clean build.