需求场景:
已经知道了Iterator<T>,然后打算通过Iterator进行简单处理后变成List<?>,这种需求还是比较常见的,MR中最为常见。
方案:
第一种方式:
直接遍历迭代获取到T然后经过业务逻辑处理之后封装成?然后放入指定的List中去
第二种方式:
采用org.apache.commons.collections.CollectionUtils.collect进行转换,需要自己实现Transformer,也提供了一些常见的实现。
实现:
依赖jar:
commons-collections 2.6 commons-lang 3.2.1
构造数据:
List<String> list = new ArrayList<String>(); for (int i = 0; i < 10; i++) { list.add(RandomStringUtils.random(10, "abc")); }
转换操作:
CollectionUtils.collect(list.iterator(), TransformerUtils.nopTransformer())
TransformerUtils提供的Transformer实现:
org.apache.commons.collections.functors.ChainedTransformer; org.apache.commons.collections.functors.CloneTransformer; org.apache.commons.collections.functors.ClosureTransformer; org.apache.commons.collections.functors.ConstantTransformer; org.apache.commons.collections.functors.EqualPredicate; org.apache.commons.collections.functors.ExceptionTransformer; org.apache.commons.collections.functors.FactoryTransformer; org.apache.commons.collections.functors.InstantiateTransformer; org.apache.commons.collections.functors.InvokerTransformer; org.apache.commons.collections.functors.MapTransformer; org.apache.commons.collections.functors.NOPTransformer; org.apache.commons.collections.functors.PredicateTransformer; org.apache.commons.collections.functors.StringValueTransformer; org.apache.commons.collections.functors.SwitchTransformer;