java list两两合并的10种方式

public static<T> List<T> merge(List<T> list1, List<T> list2)
{
    List<T> list = new ArrayList<>();
    list.addAll(list1);
    list.addAll(list2);
    return list;
}
public static<T> List<T> merge2(List<T> list1, List<T> list2)
{
    List<T> list = new ArrayList<>(list1);
    list.addAll(list2);
    return list;
}
public static<T> List<T> merge3(List<T> list1, List<T> list2)
{
    return new ArrayList<T>() {{
        addAll(list1);
        addAll(list2);
    }};
}
public static List<String> merge4(List<String> list1, List<String> list2)
{
    List<String> list = new ArrayList<>();
    Collections.addAll(list, list1.toArray(new String[0]));
    Collections.addAll(list, list2.toArray(new String[0]));
    return list;
}

public static<T> List<T> merge5(List<T> list1, List<T> list2)
{
    return Stream.of(list1, list2)
            .flatMap(x -> x.stream())
            .collect(Collectors.toList());
}

public static<T> List<T> merge6(List<T> list1, List<T> list2)
{
    List<T> list = new ArrayList<>();
    Stream.of(list1, list2).forEach(list::addAll);
    return list;
}

// Generic method to join two lists in Java
public static<T> List<T> merge7(List<T> list1, List<T> list2)
{
    List<T> list = list1.stream().collect(Collectors.toList());
    list.addAll(list2);
    return list;
}

// Generic method to join two lists in Java
public static<T> List<T> merge8(List<T> list1, List<T> list2) {
    return Lists.newArrayList(Iterables.concat(list1, list2));
}

// Generic method to join two lists in Java
public static<T> List<T> merge9(List<T> list1, List<T> list2)
{
    List<T> list = Lists.newArrayList();
    Iterables.addAll(list, list1);
    Iterables.addAll(list, list2);
    return list;
}

// Generic method to join two lists in Java
public static<T> List<T> merge10(List<T> list1, List<T> list2) {
    return ListUtils.union(list1, list2);
}