java - 将 HashMap 转换为数组

Question

我有一个 HashMap，我想将它转换成一个数组。下面的代码，我得到以下内容:[[2, 11, 10, 9], [value1, value2, value3, value4], [null, null, null, null], [null, null, null, null]]“空”条目给我一个空指针异常。为什么它是应该的两倍大？我只想要真实的条目:[[2, 11, 10, 9], [值 1, 值 2, 值 3, 值 4]]。我做错了什么？

String[][] test = getArrayFromHash(hashmap);

    public static String[][] getArrayFromHash(HashMap<String, String> hashMap){
        String[][] str = null;
        {
            Object[] keys = hashMap.keySet().toArray();
            Object[] values = hashMap.values().toArray();
            str = new String[keys.length][values.length];
            for(int i=0;i<keys.length;i++) {
                str[0][i] = (String)keys[i];
                str[1][i] = (String)values[i];
            }
        }
        return str;
    }

谢谢!

Answer 1

引用这个link:::

    String[][] arr = new String[hashmap.size()][2];
    Set entries = hashmap.entrySet();
    Iterator entriesIterator = entries.iterator();

    int i = 0;
    while(entriesIterator.hasNext()){

        Map.Entry mapping = (Map.Entry) entriesIterator.next();

        arr[i][0] = mapping.getKey().toString();
        arr[i][1] = mapping.getValue().toString();

        i++;
    }

UPdated::::: 得到两个一维数组

String[] arr1 = new String[hashmap.size()];
String[] arr2 = new String[hashmap.size()];
        Set entries = hashmap.entrySet();
        Iterator entriesIterator = entries.iterator();

        int i = 0;
        while(entriesIterator.hasNext()){

            Map.Entry mapping = (Map.Entry) entriesIterator.next();

            arr1[i] = mapping.getKey().toString();
            arr2[i] = mapping.getValue().toString();

            i++;
        }