您可以使用收集器：
import java.util.*;import java.util.stream.Collectors;public class Defensive { public static void main(String[] args) { Map<String, Column> original = new HashMap<>(); original.put("foo", new Column()); original.put("bar", new Column()); Map<String, Column> copy = original.entrySet() .stream() .collect(Collectors.toMap(Map.Entry::getKey, e -> new Column(e.getValue()))); System.out.println(original); System.out.println(copy); } static class Column { public Column() {} public Column(Column c) {} }}
