java.lang.NoClassDefFoundError：org / slf4j / Logger

Question

I am trying to run a project that uses a Logger class. Trying to do so causes the exception below. The compiler is looking for Logger at org/slf4j/Logger however in my Libraries it is located at org/apache/log4j (I am using IntelliJ). How can I fix this?

Exception in thread "main" java.lang.NoClassDefFoundError: org/slf4j/Logger
    at org.apache.logging.slf4j.SLF4JLoggerContext.getLogger(SLF4JLoggerContext.java:42)
    at org.apache.logging.log4j.LogManager.getLogger(LogManager.java:455)
    at org.apache.logging.log4j.LogManager.getLogger(LogManager.java:441)
    at activitystreamer.Client.<clinit>(Client.java:17)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:264)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:123)
Caused by: java.lang.ClassNotFoundException: org.slf4j.Logger
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 7 more

Answer 1

You missed to add SLF4J. To add SLF4j to your project, the first thing to is to add in the SLF4j API. Check https://www.slf4j.org/docs.html for more details .