集合类型转换util方法是否已存在于任何API中？

Question

interface TypeConverter<T, E> {
     T convert(E e);
}
class CollectionUtil() {
     public static <E> List<T> convertToList(List<E> fromList, TypeConverter<T, E> conv) {
     {
            if(fromList== null) return null;
            List<T> newList = new ArrayList<T>(fromList.size())  
            for(E e : fromList) 
            {
                newList.add(conv.convert(e));
            }
            return newList;
     } 
}

上面的代码解释了通过为String,Integer实现TypeConverter接口,从String of String转换为Integer List.在任何API中是否已存在任何集合转换实用程序方法,例如要设置的列表等等？

Answer 1

在番石榴:

List<String> strings = Arrays.asList("1", "2", "3");
List<Integer> integers =
        Lists.transform(strings, new Function<String, Integer>() {
            @Override
            public Integer apply(String input) {
                return Integer.parseInt(input);
            }
        });

Maven的

<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>13.0</version>
</dependency>

在Collections 15包中:

final List<Integer> integers =
        ListUtils.transformedList(strings, new Transformer<String, Integer>() {
            @Override
            public Integer transform(String s) {
                return Integer.parseInt(s);
            }
        });

Maven的

<dependency>
    <groupId>net.sourceforge.collections</groupId>
    <artifactId>collections-generic</artifactId>
    <version>4.01</version>
</dependency>

在Functional Java中

List<Integer> integers = List.list("1", "2", "3").map(new F<String, Integer>() {
    @Override
    public Integer f(String s) {
        return Integer.parseInt(s);
    }
});

Maven的

<dependency>
    <groupId>org.functionaljava</groupId>
    <artifactId>functionaljava</artifactId>
    <version>3.1</version>
</dependency>

请注意,此库使用不同的集合集.

... Scala中的奖金:

Seq("1", "2", "3") map {_.toInt}