How to hide public static final in proguard?

I have the following class

package br.com.app1.urls;

public class Urlapp {

public static final String URL_LOGAR ="url/login";

public static final String URL_CADASTRAR_INCIDENTES ="url/incidentes";

}

I would like to know how to configure in proguard to not display the url

My proguard is assm

-dontusemixedcaseclassnames
-dontskipnonpubliclibraryclasses
-dontwarn android.support.**
-verbose

-dontoptimize
-dontpreverify


-keepattributes *Annotation*
-keep public class * extends android.app.Activity
-keep public class * extends android.app.Application
-keep public class * extends android.app.Service
-keep public class * extends android.content.BroadcastReceiver
-keep public class * extends android.content.ContentProvider
-keep public class com.google.vending.licensing.ILicensingService
-keep public class com.android.vending.licensing.ILicensingService
-keep public class * extends android.support.v4.app.Fragment
-keep public class * extends android.app.Fragment

-keep class br.com.patrulhar.WS_JSON.Const { public static *; }

-keepclasseswithmembernames class * {
    native <methods>;
}

-keepclasseswithmembernames class * {
    public <init>(android.content.Context, android.util.AttributeSet);
}

-keepclasseswithmembernames class * {
    public <init>(android.content.Context, android.util.AttributeSet, int);
}

 -keepclassmembers public class * extends android.view.View {
  void set*(***);
  *** get*();
 }

-keepclassmembers enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

-keep class * implements android.os.Parcelable {
    *;
}

-keep class * implements android.os.Parcelable {
  public static final android.os.Parcelable$Creator *;
}

-keepclassmembers class **.R$* {
  public static <fields>;
}