package org.junit.rules;
   
   import static org.hamcrest.CoreMatchers.allOf;
   import static org.junit.matchers.JUnitMatchers.isThrowable;
   
   import java.util.ArrayList;
   import java.util.List;
   
   import org.hamcrest.Matcher;
  
  /**
   * Builds special matcher used by {@link ExpectedException}.
   */
  class ExpectedExceptionMatcherBuilder {
  
      private final List<Matcher<?>> matchers = new ArrayList<Matcher<?>>();
  
      void add(Matcher<?> matcher) {
          matchers.add(matcher);
      }
  
      boolean expectsThrowable() {
          return !matchers.isEmpty();
      }
  
      Matcher<Throwable> build() {
          return isThrowable(allOfTheMatchers());
      }
  
      private Matcher<Throwable> allOfTheMatchers() {
          if (matchers.size() == 1) {
              return cast(matchers.get(0));
          }
          return allOf(castedMatchers());
      }
  
      @SuppressWarnings({"unchecked", "rawtypes"})
      private List<Matcher<? super Throwable>> castedMatchers() {
          return new ArrayList<Matcher<? super Throwable>>((List) matchers);
      }
  
      @SuppressWarnings("unchecked")
      private Matcher<Throwable> cast(Matcher<?> singleMatcher) {
          return (Matcher<Throwable>) singleMatcher;
      }
  }