How to print arraylist java

Here Is 4 Ways To Print ArrayList Elements In Java

Learn 4 Techniques to PRINT ArrayList Elements in Java with Code Example.

To print elements, first we’ll create a String ArrayList and store weekdays name as strings into it and display them using following ways:

Here is a string ArrayList. We have created an object of the list and added name of week days using add() method of ArrayList.

PRINTING ARRAYLIST

1) Using for loop

To use for loop, we’re getting the length of the ArrayList using its size() method, up to which we need to retrieve elements. We have used get(i) method of the arraylist to fetch the data present at the indexes of the arraylist.

2) Using for-each loop

Here, the same for loop is written in another form using for each loop or advance loop method in java. This type of loop fetchs every elements from the arralist object one by one.

3) Using iterator

Iterators in java collection framework are used to retrieve elements one by one. ArrayList iterator() method returns an iterator for the list. The Iterator contains methods hasNext() that checks if next element is available. Another method next() of Iterator returns elements.

We have implemented while loop to traverse the ArrayList. In the loop, we are checking if next element is available using hasNext() method. Iterator hasNext() methods returns the Boolean value true or false. If hasNext() returns true, the loop fetchs the ArrayList elements using Iterator next() method and print it using System.out.println mehtod. If hasNext() returns false, there is no further elements in the list.

4) Using list-iterator

We can also use ListIterator to traverse elements of the ArrayList. ListIterator also has methods hasNext() to check if element is present and next() method to retrieve ArrayList elements. ListIterator is similar to iterator with difference that iterator is unidirectional and ListIterator is bidirectional.

The only thing in case of list iterator is that we have to initialize it with null at first.

ListIterator litr = null;

Complete Code to print ArrayList Elements in Java using all 4 Ways

The complete code to print all elements of the ArrayList using all 4 techniques is given below:

Output
Using For Loop

Using for-each loop

Using list iterator
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday

Users Question on ArrayList from comments:

Answer: NO, you can write a single method to print multiple arraylists and call the method for each array list as shown below.

Output:

Days Array List:
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Fruits Array List:
Apple
Mango
Orange

print arraylist element?

how do i print the element «e» in arraylist «list» out?

7 Answers 7

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Do you want to print the entire list or you want to iterate through each element of the list? Either way to print anything meaningful your Dog class need to override the toString() method (as mentioned in other answers) from the Object class to return a valid result.

The output of this code is:

First make sure that Dog class implements the method public String toString() then use

where index is the position inside the list. Of course since you provide your implementation you can decide how dog prints itself.

Here is an updated solution for Java8, using lambdas and streams:

Or, without joining the list into one large string:

Your code requires that the Dog class has overridden the toString() method so that it knows how to print itself out. Otherwise, your code looks correct.

You should override toString() method in your Dog class. which will be called when you use this object in sysout.

Printing a specific element is

I think the best way to print the whole list in one go and this will also avoid putting a loop

If you want to print an arraylist with integer numbers, as an example you can use below code.

The output is above code:

Not the answer you’re looking for? Browse other questions tagged java or ask your own question.

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Java print ArrayList example

Java print ArrayList example shows how to print ArrayList in Java. The example also shows various ways to print the ArrayList using a loop, Arrays class, and Java 8 Stream.

How to print ArrayList in Java?

There are several ways using which you can print ArrayList in Java as given below.

1) Using for loop

You can print ArrayList using for loop in Java just like an array.

2) Using enhanced for loop

You can also use the enhanced for loop instead of the for loop it iterate over the elements of an ArrayList and print.

3) Using Arrays class

You can convert ArrayList to an array and use the toString method of Arrays class to print the elements.

If you want to remove the square brackets, you can remove them using the replaceAll method as given below.

4) Using Java 8 stream

If you are using Java 8, you can use the stream as given below.

Or you can use below given statement to print the elements of ArrayList.

How to print ArrayList containing custom objects?

How to print ArrayList containing objects of a custom class? For example, consider below given code containing ArrayList of Person class objects.

aListPerson = new ArrayList

Instead of printing the contents of the Person objects, our code printed memory locations of the Person object. The reason is since the Person class does not override the toString method, the default toString method of the Object class is called which prints the address location of the object.

Let’s override the toString method in the Person class to get the contents of the Person object instead of the memory locations.

How to print out all the elements of a List in Java?

This is my printing code.

Could anyone please help me why it isn’t printing the value of the elements.

23 Answers 23

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The following is compact and avoids the loop in your example code (and gives you nice commas):

However, as others have pointed out, if you don’t have sensible toString() methods implemented for the objects inside the list, you will get the object pointers (hash codes, in fact) you’re observing. This is true whether they’re in a list or not.

Since Java 8, List inherits a default «forEach» method which you can combine with the method reference «System.out::println» like this:

Here is some example about getting print out the list component:

Returns a string representation of this collection. The string representation consists of a list of the collection’s elements in the order they are returned by its iterator, enclosed in square brackets («[]»). Adjacent elements are separated by the characters «, » (comma and space). Elements are converted to strings as by String.valueOf(Object).

See the below example:

Use String.join() for example:

The Java 8 Streams approach.

The objects in the list must have toString implemented for them to print something meaningful to screen.

Here’s a quick test to see the differences:

And when this executes, the results printed to screen are:

Since T1 does not override the toString method, its instance t1 prints out as something that isn’t very useful. On the other hand, T2 overrides toString, so we control what it prints when it is used in I/O, and we see something a little better on screen.

Or you could simply use the Apache Commons utilities:

Consider a List stringList which can be printed in many ways using Java 8 constructs:

How are these approaches different from each other?

First Approach ( Iterable.forEach )- The iterator of the collection is generally used and that is designed to be fail-fast which means it will throw ConcurrentModificationException if the underlying collection is structurally modified during the iteration. As mentioned in the doc for ArrayList :

A structural modification is any operation that adds or deletes one or more elements, or explicitly resizes the backing array; merely setting the value of an element is not a structural modification.

So it means for ArrayList.forEach setting the value is allowed without any issue. And in case of concurrent collection e.g. ConcurrentLinkedQueue the iterator would be weakly-consistent which means the actions passed in forEach are allowed to make even structural changes without ConcurrentModificationException exception being thrown. But here the modifications might or might not be visible in that iteration.

Second Approach ( Stream.forEach )- The order is undefined. Though it may not occur for sequential streams but the specification does not guarantee it. Also the action is required to be non-interfering in nature. As mentioned in doc:

The behavior of this operation is explicitly nondeterministic. For parallel stream pipelines, this operation does not guarantee to respect the encounter order of the stream, as doing so would sacrifice the benefit of parallelism.

Third Approach ( Stream.forEachOrdered )- The action would be performed in the encounter order of the stream. So whenever order matters use forEachOrdered without a second thought. As mentioned in the doc:

Performs an action for each element of this stream, in the encounter order of the stream if the stream has a defined encounter order.

While iterating over a synchronized collection the first approach would take the collection’s lock once and would hold it across all the calls to action method, but in case of streams they use collection’s spliterator, which does not lock and relies on the already established rules of non-interference. In case collection backing the stream is modified during iteration a ConcurrentModificationException would be thrown or inconsistent result may occur.

Java print Arraylist

I have three classes, BankLogic, Customer and SavingsAccount. I want to print out an arraylist of all the customers, but I’m only getting a blank result. This should be the simplest thing to do, but i can’t get it to work. What am I doing wrong?

This is how it looks in BankLogic:

My Customer class:

3 Answers 3

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First of all debug your program and see if the ArrayLists aren’t empty. If they aren’t good, if they are empty then there must something wrong with your code.

And I think you’ve made your classes wrong.

You need to call BankLogic infoCustomer() after putting some objects in the customerlist.

like you shoudn’t use constructor to initialize the customerlist,better u can send a customerlist in this constructor as below

In the main method fromwhere you are calling this method you can add customer there

There is a problem with your addCustomer method. what you are doing is that from your current code you never add any of the customers to the List before running your test methods in BankMenu class. So change the addCustomer method from