Hamcrest Matchers包含匹配器列表

Question

我正在尝试使用org.hamcrest.Matchers.contents（java.util.List<Matcher<？superE>>），但编译器告诉我它无法解析该方法。

我甚至尝试了Hamcrest在这里给出的例子，但我得到了相同的编译错误：

assertThat(Arrays.asList("foo", "bar"), contains(Arrays.asList(equalTo("foo"), equalTo("bar"))));
Error:(13, 9) java: no suitable method found for assertThat(java.util.List<java.lang.String>,org.hamcrest.Matcher<java.lang.Iterable<? extends java.util.List<org.hamcrest.Matcher<java.lang.String>>>>)
method org.hamcrest.MatcherAssert.<T>assertThat(T,org.hamcrest.Matcher<? super T>) is not applicable
  (actual argument org.hamcrest.Matcher<java.lang.Iterable<? extends java.util.List<org.hamcrest.Matcher<java.lang.String>>>> cannot be converted to org.hamcrest.Matcher<? super java.util.List<java.lang.String>> by method invocation conversion)
method org.hamcrest.MatcherAssert.<T>assertThat(java.lang.String,T,org.hamcrest.Matcher<? super T>) is not applicable
  (cannot instantiate from arguments because actual and formal argument lists differ in length)
method org.hamcrest.MatcherAssert.assertThat(java.lang.String,boolean) is not applicable
  (actual argument java.util.List<java.lang.String> cannot be converted to java.lang.String by method invocation conversion)

我试图将第二个参数转换为Matcher<？超级列表<字符串>gt；

assertThat(Arrays.asList("foo", "bar"), (Matcher<? super List<String>>)contains(Arrays.asList(equalTo("foo"), equalTo("bar"))));

但后来我得到了另一个编译错误：

Error:(16, 88) java: inconvertible types  
required: org.hamcrest.Matcher<? super java.util.List<java.lang.String>> 
found:    org.hamcrest.Matcher<java.lang.Iterable<? extends java.util.List<org.hamcrest.Matcher<java.lang.String>>>>

有没有办法正确使用这种方法？

Answer 1

问题是Arrays.asList(equalTo("foo"), equalTo("bar"));会给您类型List<Matcher<String>>，但您确实想要List<Matcher<? super String>>。您必须明确指定类型：

assertThat(str, 
    contains(Arrays.<Matcher<? super String>>asList(
        equalTo("foo"), 
        equalTo("bar"))));