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Java AbstractMap.SimpleEntry toString() Method

Last Updated : 21 Jan, 2025
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In Java, the toString() method of the AbstractMap.SimpleEntry class is used to return a string representation of the key-value pair in the format key=value. If the key or value is null, it is represented as the string null. This method is used to provide a straightforward way to display the contents of the SimpleEntry object.

Example 1: Here, the toString() method of AbstraceMap.SimpleEntry class is used to print key-value pairs stored in a List.

Java
// Java program to demonstrate
// AbstractMap.SimpleEntry.toString() method
import java.util.*;
import java.util.AbstractMap.SimpleEntry;

public class Geeks {

    @SuppressWarnings({ "unchecked", "rawtypes" })
    public static void main(String[] args)
    {

        // create a ArrayList of Map
        ArrayList<
            AbstractMap.SimpleEntry<Integer, Integer> >
            al
            = new ArrayList<AbstractMap.SimpleEntry<
                Integer, Integer> >();

        // add values
        al.add(new AbstractMap.SimpleEntry(0, 100));
        al.add(new AbstractMap.SimpleEntry(1, 200));
        al.add(new AbstractMap.SimpleEntry(2, 300));

        for (int i = 0; i < al.size(); i++) {

            // get map from list
            AbstractMap.SimpleEntry<Integer, Integer> m
                = al.get(i);

            // get representation of map using toString()
            String value = m.toString();

            System.out.println(value);
        }
    }
}

Output
0=100
1=200
2=300

Explanation: This example stores key-value pair in an ArrayList using AbstractMap.simpleEntry and print them using toString() method, which display the pais in key=value format.

Syntax of toString() Method

public String toString()

Return Type: This method returns a string that represents the key-value pair in the SimpleEntry object.

Example 2: Here, the AbstractMap.SimpleEntry includes null as a key in its string representation when no key is provided.

Java
// Java program to demonstrates that AbstractMap.SimpleEntry
// allows null as a key and prints it as null=Value
import java.util.AbstractMap.SimpleEntry;

public class Geeks {
    public static void main(String[] args)
    {
        // Create a SimpleEntry with a null key
        SimpleEntry<String, String> e
            = new SimpleEntry<>(null, "Value");

        // Print the entry
        System.out.println(e);
    }
}

Output
null=Value

Explanation: In this example, we create a SimpleEntry object with a null key and a value “Value”. The output is null=Value demonstrating that SimpleEntry includes null in its string representation.



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