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不实现equals方法的情况下比较java list
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不实现equals方法的情况下比较java list
java里比较两个list的值是否一致，不考虑顺序，有多种方法，比如排序后直接用equals比较，相互之间执行两次containsAll等，这些办法都需要我们给list的元素类实现equals和hashcode方法。但是有一种特殊情况，如果我们并不方便去实习类的equals方法，例如是一个古老的第三方jar包，改代码会带来很多未知问题，这时候该怎么办呢。
其实很简单，万能的apache-commons早就想到了这一点，所以在commons-collections4中增加了外部输入equals和hashcode的方法，甚至equals和hashcode方法本身也不需要我们自己写代码，可以用comons-lang包实现，具体代码如下
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-collections4</artifactId>
<version>4.1</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.5</version>
</dependency>
public static <T> boolean isEqualCollection(Collection<T> l1, Collection<T> l2, final String... exludedFields) {
Equator<T> equator = generateEquator(exludedFields);
return CollectionUtils.isEqualCollection(l1, l2, equator);
}
private static <T> Equator<T> generateEquator(final String... exludedFields) {
Equator<T> equator = new Equator<T>() {
@Override
public boolean equate(T o1, T o2) {
if (o1 == null && o2 == null) {
return true;
}
if (o1 == null || o2 == null) {
return false;
}
if (o1.getClass() != o2.getClass()) {
return false;
}
return EqualsBuilder.reflectionEquals(o1, o2, exludedFields);
}
@Override
public int hash(T o) {
return HashCodeBuilder.reflectionHashCode(o, exludedFields);
}
};
return equator;
}
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