How To Remove An Element From An ArrayList?
In this article, we will see how to remove an element from an ArrayList In Java.
Introduction
We have seen how we can add an element to an ArrayList and how we can change the elements of an ArrayList, now we will see how we can remove an element from an ArrayList.
To remove an element from an ArrayList, we use the remove() method.
Using the ‘ Remove (Object o)` method, we can remove the specified object from an ArrayList.
Using the remove(int index) method, we can remove the object at the specified index from an ArrayList.
Let’s see both methods one by one.
1. Remove an element from an ArrayList using the remove(Object o) method
The remove(Object o) method removes the first occurrences of the specified object from the ArrayList.
If the specified object o is not present in the ArrayList, the ArrayList remains unchanged.
The method signature is as public boolean remove(Object o)
The remove(Object o) method has a return type as a boolean. It returns true if it found an occurrence of the specified object and if it removes. Otherwise, it returns false.
We will see a Java program to remove an element from the ArrayList using the remove(Object o) method.
Example 1
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import java.util.ArrayList;
/**
* A Java program to remove an element from ArrayList
* using the remove(Object o) method.
*
* @author coderolls.com
*
*/
public class ArrayListRemoveExample {
public static void main(String[] args) {
ArrayList<String> arrayList = new ArrayList<String>();
//adding elements to the ArrayList using the normal add() method
arrayList.add("Red");
arrayList.add("Green");
arrayList.add("Pink");
System.out.println("ArrayList before removing an element"+ arrayList); // ArrayList before removing an element[Red, Green, Pink]
//Remove "Pink" from the ArrayList
arrayList.remove("Pink");
System.out.println("ArrayList after removing an element"+ arrayList);// ArrayList after removing an element[Red, Green]
}
}
Output:
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ArrayList before removing an element[Red, Green, Pink]
ArrayList after removing an element[Red, Green]
Example 2
In the above example, we have removed the string object. In this example, we will take an employee object. The Employee.java will look like the given below
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/**
* An employee class for ArrayList remove example
* @author coderolls.com
*
*/
public class Employee {
private int id;
private String name;
private int salary;
// a constructor will all the fields
public Employee(int id, String name, int salary) {
this.id = id;
this.name = name;
this.salary = salary;
}
// getters and setters for the variables
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getSalary() {
return salary;
}
public void setSalary(int salary) {
this.salary = salary;
}
// Override to string method to print student objects
@Override
public String toString() {
return "{"+this.getId()+", "+ this.getName()+ ", "+this.getSalary()+"}";
}
}
Now, we will create an ArrayList of the above employee objects and try to remove them from the arraylist using remove(Object o).
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import java.util.ArrayList;
/**
* A Java program to remove an object from ArrayList
* using the remove(int index) method.
*
* @author coderolls.com
*
*/
public class ArrayListRemoveObjectExample {
public static void main(String[] args) {
ArrayList<Employee> arrayList = new ArrayList<Employee>();
//create Employee objects
Employee john = new Employee(100, "John Doe", 20000);
Employee nathasha = new Employee(101, "Natasha Putin", 28000);
Employee remo = new Employee(102, "Remo Smith", 40000);
//adding employee objects to the arrayList using the normal add method
arrayList.add(john);
arrayList.add(nathasha);
arrayList.add(remo);
System.out.println("ArrayList before removing an employee Object:\n"+ arrayList);
//Remove object using the remo0ve(Object o) method
//Remove employee nathasha from the arrayList
arrayList.remove(nathasha);
System.out.println("\nArrayList after removing an employee Object:\n"+ arrayList);
}
}
Output:
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ArrayList before removing an employee Object:
[{100, John Doe, 20000}, {101, Natasha Putin, 28000}, {102, Remo Smith, 40000}]
ArrayList after removing an employee Object:
[{100, John Doe, 20000}, {102, Remo Smith, 40000}]
2. Remove an element from an ArrayList using the remove(int index) method
The remove(int index) removes an element at the specified position from the ArrayList.
The method signature is as public E remove(int index)
Once we remove an element from the ArrayList using the remove(int index) method, the remaining elements after the specified index get shifted left and its indices are updated.
The return type is an E. It returns the element that was removed from the list.
We will see a Java program to remove an element from the ArrayList by passing its index as an argument to the remove(int index) method.
Example 1
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import java.util.ArrayList;
/**
* A Java program to remove an element from ArrayList
* using the remove(int index) method.
*
* @author coderolls.com
*
*/
public class ArrayListRemoveExample2 {
public static void main(String[] args) {
ArrayList<String> arrayList = new ArrayList<String>();
//adding elements to the arrayList using normal add method
arrayList.add("Apple");
arrayList.add("Orange");
arrayList.add("Guava");
arrayList.add("Banana");
System.out.println("ArrayList before removing an element"+ arrayList);
// ArrayList before removing an element[Apple, Orange, Guava, Banana]
//Remove the element at the specified index i.e. 2
//Remove "Guava" from the arrayList
arrayList.remove(2);
System.out.println("ArrayList after removing an element"+ arrayList);
// ArrayList after removing an element[Apple, Orange, Banana]
}
}
Output:
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ArrayList before removing an element[Apple, Orange, Guava, Banana]
ArrayList after removing an element[Apple, Orange, Banana]
Example 2
In the above example, we have removed the string object. In this example, we will take an employee object. The Employee.java will look like the given below
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/**
* An employee class for ArrayList remove example
* @author coderolls.com
*
*/
public class Employee {
private int id;
private String name;
private int salary;
// a constructor will all the fields
public Employee(int id, String name, int salary) {
this.id = id;
this.name = name;
this.salary = salary;
}
// getters and setters for the variables
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getSalary() {
return salary;
}
public void setSalary(int salary) {
this.salary = salary;
}
// Override to string method to print student objects
@Override
public String toString() {
return "{"+this.getId()+", "+ this.getName()+ ", "+this.getSalary()+"}";
}
}
Now, we will create an arraylist of the above employee objects and try to remove them from the arraylist using remove(int index).
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import java.util.ArrayList;
/**
* A Java program to remove an object from ArrayList
* using the remove(int index) method.
*
* @author coderolls.com
*
*/
public class ArrayListRemoveObjectExample2 {
public static void main(String[] args) {
ArrayList<Employee> arrayList = new ArrayList<Employee>();
//create Employee objects
Employee john = new Employee(100, "John Doe", 20000);
Employee nathasha = new Employee(101, "Natasha Putin", 28000);
Employee remo = new Employee(102, "Remo Smith", 40000);
//adding employee objects to the arrayList using the normal add method
arrayList.add(john);
arrayList.add(nathasha);
arrayList.add(remo);
System.out.println("ArrayList before removing an employee Object:\n"+ arrayList);
//Remove object using the remove(int index) method
//Remove employee nathasha from the arrayList, so pass Natasha's index
arrayList.remove(1);
System.out.println("\nArrayList after removing an employee Object:\n"+ arrayList);
}
}
Output:
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ArrayList before removing an employee Object:
[{100, John Doe, 20000}, {101, Natasha Putin, 28000}, {102, Remo Smith, 40000}]
ArrayList after removing an employee Object:
[{100, John Doe, 20000}, {102, Remo Smith, 40000}]
Conclusion
We can remove an element from the ArrayList in two ways.
remove(Object o)- we can remove the specified object from the ArrayListremove(int index)- We can remove an element at the position (index) specified
The example Java programs given in the above tutorial can be found at this GitHub Repository.
If you know any other way, please comment below.
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