将Hashmap分配给Hashmap

您要做的不是创建地图的副本，而是创建地图的副本。当两个引用指向同一对象时，对一个对象的更改将在另一个对象中反映出来。

解决方案1：如果这是从某种简单类型到另一种类型的Map，则应改为：

Map<SomeType, OtherType> map1 = new HashMap<SomeType, OtherType>(original);

这称为复制构造函数。几乎所有标准的Collection和Map实现都有一个，通常是克隆简单结构的最简单方法。这将正常工作，只要

SomeType

OtherType

Integer

Number

Boolean

String

否则，正如其他答复者和评论者所指出的那样，您还需要复制地图值。

解决方案2：这是一个快速而又肮脏的版本，应该是安全的：

Map<Integer, Map<String, Object>> original=new HashMap<Integer, Map<String,Object>>();Map<Integer, Map<String, Object>> copy =         new HashMap<Integer, Map<String, Object>>();for(Entry<Integer, Map<String, Object>> entry : original.entrySet()){    copy.put(entry.getKey(), new HashMap<String, Object>(entry.getValue()));}

但是实际上，我喜欢Hunter提供深层复制方法的想法。因此，这里是解决方案3：使用通用参数的我自己的版本：

public static <K1, K2, V> Map<K1, Map<K2, V>> deepCopy(    Map<K1, Map<K2, V>> original){    Map<K1, Map<K2, V>> copy = new HashMap<K1, Map<K2, V>>();    for(Entry<K1, Map<K2, V>> entry : original.entrySet()){        copy.put(entry.getKey(), new HashMap<K2, V>(entry.getValue()));    }    return copy;}

您可以这样称呼它：

Map<Integer, Map<String, Object>> original=new HashMap<Integer, Map<String,Object>>();// do stuff hereMap<Integer, Map<String, Object>> copy = deepCopy(original);

更新资料

我在一起学习了一个类，该类对Maps，Collections和Array（原始和其他）执行深度克隆。用法：

Something clone = DeepClone.deepClone(original);

这里是：

public final class DeepClone {    private DeepClone(){}    public static <X> X deepClone(final X input) {        if (input == null) { return input;        } else if (input instanceof Map<?, ?>) { return (X) deepCloneMap((Map<?, ?>) input);        } else if (input instanceof Collection<?>) { return (X) deepCloneCollection((Collection<?>) input);        } else if (input instanceof Object[]) { return (X) deepCloneObjectArray((Object[]) input);        } else if (input.getClass().isArray()) { return (X) clonePrimitiveArray((Object) input);        }        return input;    }    private static Object clonePrimitiveArray(final Object input) {        final int length = Array.getLength(input);        final Object copy = Array.newInstance(input.getClass().getComponentType(), length);        // deep clone not necessary, primitives are immutable        System.arraycopy(input, 0, copy, 0, length);        return copy;    }    private static <E> E[] deepCloneObjectArray(final E[] input) {        final E[] clone = (E[]) Array.newInstance(input.getClass().getComponentType(), input.length);        for (int i = 0; i < input.length; i++) { clone[i] = deepClone(input[i]);        }        return clone;    }    private static <E> Collection<E> deepCloneCollection(final Collection<E> input) {        Collection<E> clone;        // this is of course far from comprehensive. extend this as needed        if (input instanceof linkedList<?>) { clone = new linkedList<E>();        } else if (input instanceof SortedSet<?>) { clone = new TreeSet<E>();        } else if (input instanceof Set) { clone = new HashSet<E>();        } else { clone = new ArrayList<E>();        }        for (E item : input) { clone.add(deepClone(item));        }        return clone;    }    private static <K, V> Map<K, V> deepCloneMap(final Map<K, V> map) {        Map<K, V> clone;        // this is of course far from comprehensive. extend this as needed        if (map instanceof linkedHashMap<?, ?>) { clone = new linkedHashMap<K, V>();        } else if (map instanceof TreeMap<?, ?>) { clone = new TreeMap<K, V>();        } else { clone = new HashMap<K, V>();        }        for (Entry<K, V> entry : map.entrySet()) { clone.put(deepClone(entry.getKey()), deepClone(entry.getValue()));        }        return clone;    }}