How to create a List of Dictionaries in Java - Step by Step Examples

How to create a List of Dictionaries in Java ?

Answer

In Java, you can create a list of dictionaries using the `ArrayList` class for the outer list and `HashMap` class for the inner dictionaries.

✐ Examples

1 Create List of Dictionaries

In this example,

We create two inner dictionaries named dict1 and dict2 using the HashMap class.
We create an outer list named listOfDicts using the ArrayList class and initialize it with the inner dictionaries.
Finally, we print the list of dictionaries to standard output.

Java Program

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Main {
    public static void main(String[] args) {
        Map<String, String> dict1 = new HashMap<>();
        dict1.put("key1", "value1");
        dict1.put("key2", "value2");

        Map<String, String> dict2 = new HashMap<>();
        dict2.put("key3", "value3");
        dict2.put("key4", "value4");

        List<Map<String, String>> listOfDicts = new ArrayList<>();
        listOfDicts.add(dict1);
        listOfDicts.add(dict2);

        System.out.println(listOfDicts);
    }
}

Output

[{key1=value1, key2=value2}, {key3=value3, key4=value4}]

2 Create List of Dictionaries with Empty Inner Dictionaries

In this example,

We create an empty outer list named listOfDictsEmpty using the ArrayList class.
We create two empty inner dictionaries named dict3 and dict4 using the HashMap class.
We use the add method to add the inner dictionaries dict3 and dict4 to the outer list listOfDictsEmpty.
Finally, we print the list of dictionaries with empty inner dictionaries to standard output.

Java Program

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Main {
    public static void main(String[] args) {
        List<Map<String, String>> listOfDictsEmpty = new ArrayList<>();

        Map<String, String> dict3 = new HashMap<>();
        Map<String, String> dict4 = new HashMap<>();

        listOfDictsEmpty.add(dict3);
        listOfDictsEmpty.add(dict4);

        System.out.println(listOfDictsEmpty);
    }
}

Output

[{}, {}]

Summary

In this tutorial, we learned How to create a List of Dictionaries in Java language with well detailed examples.

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How to create a List of Dictionaries in Java - Step by Step Examples

How to create a List of Dictionaries in Java ?

Answer

✐ Examples

1 Create List of Dictionaries

Java Program

Output

2 Create List of Dictionaries with Empty Inner Dictionaries

Java Program

Output

Summary

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