Collections replaceAll() Method in Java with Examples

The replaceAll() method of java.util.Collections class is used to replace all occurrences of one specified value in a list with another. More formally, replaces with newVal each element e in the list such that 

oldVal == null ? e==null : oldVal.equals(e) 

Note: This method has no effect on the size of the list.

Parameters: This method takes the following argument as a Parameter  

• list: The list in which replacement is to occur.
• oldVal: The old value to be replaced.
• newVal: The new value with which oldVal is to be replaced.

Return Value: This method returns true if the list contained one or more elements e such that as shown below else false 

oldVal== null ? e==null : oldVal.equals(e)

Syntax:

public static  boolean replaceAll(List list, T oldVal, T newVal)

Example 1:

Java

// Java program to demonstrate
// replaceAll() method for String value

// Importing utility classes
import java.util.*;

// Main class
public class GFG {

    // Main driver method
    public static void main(String[] argv) throws Exception
    {

        // Try block to check for exceptions
        try {

            // Creating a vector object of string type
            List<String> vector = new Vector<String>();

            // Populating the above Vector object
            // Custom input elements
            vector.add("A");
            vector.add("B");
            vector.add("A");
            vector.add("C");

            // Printing the vector
            System.out.println("Initial Vector :" + vector);

            // Replacing value
            // using replaceAll() method
            Collections.replaceAll(vector, "A", "TAJMAHAL");

            // Printing elements of Vector object after
            // replacing
            System.out.println("Vector after replace :"
                               + vector);
        }

        // Catch block to handle the exceptions
        catch (IllegalArgumentException e) {

            // Display message when exception occurs
            System.out.println("Exception thrown : " + e);
        }
    }
}

Output

Initial Vector :[A, B, A, C]
Vector after replace :[TAJMAHAL, B, TAJMAHAL, C]

Example 2:

Java

// Java program to demonstrate
// replaceAll() method for Integer value

// importing utility classes
import java.util.*;

// Main class
public class GFG {

    // Main driver method
    public static void main(String[] argv) throws Exception
    {

        // Try block to check for exceptions
        try {

            // Creating object of List<String>
            List<Integer> vector = new Vector<Integer>();

            // Populate the vector
            vector.add(20);
            vector.add(30);
            vector.add(20);
            vector.add(30);

            // Printing the vector before replacing
            // elements
            System.out.println("Initial values are :"
                               + vector);

            // Replacing value
            // using replaceAll() method
            Collections.replaceAll(vector, 20, 400);

            // Printing the vector after replacing elements
            System.out.println("Value after replace :"
                               + vector);
        }

        // Catch block to handle IllegalArgumentException
        catch (IllegalArgumentException e) {

            // Display the exceptions on the console
            System.out.println("Exception thrown : " + e);
        }
    }
}

Output:

Initial values are :[20, 30, 20, 30]
Value after replace :[400, 30, 400, 30]