import org.jetbrains.annotations.Contract;
import org.jetbrains.annotations.Nullable;

import java.lang.*;
import java.lang.AssertionError;
import java.lang.IllegalArgumentException;

public class AssertIsNotNull {
  void bar(String s) {
    if (<warning descr="Condition 's == null && trimIfNotNull(s) != null' is always 'false'">s == null && <warning descr="Condition 'trimIfNotNull(s) != null' is always 'false' when reached">trimIfNotNull(s) != null</warning></warning>) {
      throw new AssertionError();
    }

    final Object o = call();
    assertIsNotNull(o);
    if(<warning descr="Condition 'o == null' is always 'false'">o == null</warning>) {}
  }
  
  @Contract("null -> fail")
  static void assertIsNotNull(Object o) {
    if (o == null) {
      throw new IllegalArgumentException();
    }
  }

  @Contract("null -> null; !null -> !null")
  @Nullable static String trimIfNotNull(@Nullable String s) {
    if (s == null) {
      return null;
    }
    return s.trim();
  }
  
  Object call() {return new Object();}
  
  @Contract(<warning descr="A contract clause must be in form arg1, ..., argN -> return-value">"a"</warning>)
  void malformedContract() {}

  @Contract(<warning descr="Method takes 2 parameters, while contract clause 0 expects 1">"null -> _"</warning>)
  void wrongParameterCount(Object a, boolean b) {}
}