tonek

package test;

import org.jetbrains.annotations.NotNull;

public class Test {
    public static void main(String[] args) {
        notNull(null);
    }

    private static void notNull(@NotNull String arg) {

tonek

package test;

import org.jetbrains.annotations.Nullable;
import org.jetbrains.annotations.NotNull;

public class Simple {
  public String testMethod(int a, @NotNull String v, @Nullable String b) {
    return null;
  }
}

tonek

package test;

public class Simple {
  public String testMethod(int a, String v, String b) {
    if (v == null) {
      throw new IllegalArgumentException("Argument 1 for @NotNull parameter of test/Simple.testMethod must not be null");
    }
    return null;
  }
}