ArrayList — Most Important Methods

Below are some important methods to know
1. boolean add(E e);
2. void add(int index, E element);
3. boolean addAll(Collection<? extends E> c);
4. boolean addAll(int index, Collection<? extends E> c);
5. E remove(int index);
6. boolean remove(Object o);
7. boolean removeAll(Collection<?> c);
8. default boolean removeIf(Predicate<? super E> filter)
9. boolean removeAll(Collection<?> c);

Example to cover all above methods:-

package com.demo.collections;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.function.Predicate;
public class ArrayListMethods {
public static void main(String[] args) {
List<String> movieList = new ArrayList<>();
movieList.add(“Hero”);
movieList.add(“Disco”);
movieList.add(“Love”);
movieList.add(“Friendship”);
movieList.add(“Dragon”);
System.out.println(“===Printing full list===”);
System.out.println(movieList);
movieList.add(2, “Dancer”);
System.out.println(“===Printing list after adding at index 2===”);
System.out.println(movieList);
List<String> oldList = new ArrayList<>();
oldList.add(“Indus”);
oldList.add(“Civil war”);
System.out.println(“===Adding collection to another collection===”);
movieList.addAll(oldList);
System.out.println(movieList);
System.out.println(“===Adding collection to another collection at particular index===”);
List<String> newList = new ArrayList<>();
newList.add(“Baggi”);
newList.add(“Tigers”);
movieList.addAll(4, newList);
System.out.println(movieList);
System.out.println(“===Removing element by index===”);
String el = movieList.remove(3);
System.out.println(“Element Going To Remove is:” + el);
System.out.println(movieList);
System.out.println(“===Removing element by index with object===”);
boolean removeFlag = movieList.remove(“Indus”);
System.out.println(“removeFlag:” + removeFlag);
System.out.println(movieList);
System.out.println(“===Removing element by collection===”);
List<String> listToRemove = Arrays.asList(“Dragon”, “Tigers”);
movieList.removeAll(listToRemove);
System.out.println(movieList);
System.out.println(“===Remove element by using predicate===”);
movieList.removeIf(new Predicate<String>() {
@Override
public boolean test(String t) {
return t.startsWith(“B”);
}
});
System.out.println(movieList);
System.out.println(“===Remove by another collection===”);
movieList.removeAll(Arrays.asList(“Civil war”, “Disco”));
System.out.println(movieList);
}
}

Output:-

===Printing full list===
[Hero, Disco, Love, Friendship, Dragon]
===Printing list after adding at index 2===
[Hero, Disco, Dancer, Love, Friendship, Dragon]
===Adding collection to another collection===
[Hero, Disco, Dancer, Love, Friendship, Dragon, Indus, Civil war]
===Adding collection to another collection at particular index===
[Hero, Disco, Dancer, Love, Baggi, Tigers, Friendship, Dragon, Indus, Civil war]
===Removing element by index===
Element Going To Remove is:Love
[Hero, Disco, Dancer, Baggi, Tigers, Friendship, Dragon, Indus, Civil war]
===Removing element by index with object===
removeFlag:true
[Hero, Disco, Dancer, Baggi, Tigers, Friendship, Dragon, Civil war]
===Removing element by collection===
[Hero, Disco, Dancer, Baggi, Friendship, Civil war]
===Remove element by using predicate===
[Hero, Disco, Dancer, Friendship, Civil war]
===Remove by another collection===
[Hero, Dancer, Friendship]

=============== Happy Learning ================