error,how to solve this?

[naniminmin]

Exception in thread "main" java.lang.reflect.InvocationTargetException at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:568) at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:58) Caused by: java.lang.NoClassDefFoundError: org/bitcoinj/core/ECKey at btc.btc2.btc.main(btc.java:28) ... 5 more Caused by: java.lang.ClassNotFoundException: org.bitcoinj.core.ECKey at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:445) at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:587) at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520) ... 6 more