Java: how to convert HashMap<String, Object> to array

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I need to convert a HashMap<String, Object> to an array; could anyone show me how it's done?

14 Answers
hashMap.keySet().toArray(); // returns an array of keys
hashMap.values().toArray(); // returns an array of values

Edit

It should be noted that the ordering of both arrays may not be the same, See oxbow_lakes answer for a better approach for iteration when the pair key/values are needed.

If you want the keys and values, you can always do this via the entrySet:

hashMap.entrySet().toArray(); // returns a Map.Entry<K,V>[]

From each entry you can (of course) get both the key and value via the getKey and getValue methods

If you are using Java 8+ and need a 2 dimensional Array, perhaps for TestNG data providers, you can try:

map.entrySet()
    .stream()
    .map(e -> new Object[]{e.getKey(), e.getValue()})
    .toArray(Object[][]::new);

If your Objects are Strings and you need a String[][], try:

map.entrySet()
    .stream()
    .map(e -> new String[]{e.getKey(), e.getValue().toString()})
    .toArray(String[][]::new);

In the case keys and values are strings and you want to alternate key and value in the same array:

String[] result = myMap.entrySet()
                       .stream()
                       .flatMap(entry -> Stream.of(entry.getKey(),entry.getValue()))
                       .toArray(String[]::new);
// result = {key_1, value_1, key_2, value_2 ...}

You may try this too.

public static String[][] getArrayFromHash(Hashtable<String,String> data){
        String[][] str = null;
        {
            Object[] keys = data.keySet().toArray();
            Object[] values = data.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;
    }

Here I am using String as return type. You may change it to required return type by you.

if you need to pass values to an array of objects try:

Array:
Object[] object= hashMap.values().toArray(new Object[0]);

Arraylist:
ArrayList<Object> object=new ArrayList<>(hashMap.values());
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