How to Print array in Java?
A Java array is a data structure that allows us to hold components of the same data type. An array's items are kept in a single memory region. As a result, we may use an array to hold a fixed set of elements. In Java, we cannot print array elements directly; instead, we must utilise Arrays. deepToString() or function toString() { [native code] }() to print array elements. If we wish to print a one-dimensional array, use the function toString() { [native code] }() function; if we need to print a two-dimensional or three-dimensional array, use the deepToString() method. Java arrays enable programmers to store data of a same type. This homogeneous data structure contains information in a single memory region. Printing the array elements reveals the values contained within the Java array.
However, with Java, we cannot directly print array elements. Java has several methods for printing a two-dimensional array, such as nested for-loops, for-each loops, arrays.deepToString() function, and so on. Each method follows a different strategy, but they all achieve the same goal: printing a 2D array. We define a function called Print array(), which takes as input the array to be printed as well as its size. As mentioned in previous sections, the method internally employs a for loop to output an array. f the passed-in object is null, the function returns null; otherwise, it calls obj.toString(). To print the output, System.out.println() eventually calls function toString().
If the class of that object does not override the implementation of Object.toString(), the function will be called getClass is returned by Object.toString() ().getName()+‘@’+Integer.hashCode() = toHexString() It just returns "class name @ object's hash code."The [says that this is an array, and I stands for int in our previous output [I@74a14482 ]. (the type of the array). The array's hash code is represented in unsigned hexadecimal as 74a14482.It is recommended practise to override the Object.toString() method whenever we create our own custom classes.
Arrays cannot be printed in Java using a simple System.function out.println(). We'll be using the function toString() method of the Arrays class in Java's util package. This technique assists us in obtaining the array's String representation. This string can be simply printed using the print() or println() methods. They were provided as convenience ways to eliminate the requirement for you to design a manual for loop.In the case of ArrayLists created with primitive data types, the println command can be used directly. String, integer, float, long, double, and boolean are examples of primitive data types in Java. This method cannot be used to print a list that contains data that does not match these types.
In Java, you may print an array in the following ways:
- for loop in Java
- For-each loop in Java
- Arrays.toString() function in Java
- deepToString() function in Java
- Arrays.asList() function in Java
- Java Iterator API Java Stream API
For loop in Java:
A for loop in Java is used to run a series of instructions repeatedly until a specific condition is met.
In the following example, we've built a four-element array and initialised it. We used a for loop to retrieve the data from the array. It is the most commonly used method for printing arrays in Java.
PrintArrExample.java
public class PrintArrExample
{
public static void main(String args[])
{
//declaring and instantiating of array
int a[]=new int[3];
//initializing elements
a[0]=10;
a[1]=20;
a[2]=50;
// using for loop transverse
for(int i=0;i<a.len;i++)
System.out.println(a[i]);
}
}
Output:
10
20
50
Using Java For-each loop:
The for-each loop in Java is also used to explore an array or collection. It operates on an elemental level. It returns elements in the defined variable one by one.
In the following example, we built a String array of length four and initialised it with elements. To explore the array, we utilised a for-each loop.
PrintArrExample.java
public class PrintArrExample
{
public static void main(String args[])
{
// declaring and instantiating of array
Str[] city = new Str[3];
//elements initialization
c[0] = "Hyderabad";
c[1] = "Goa";
c[2] = "Mumbai";
// array using for-each loop transversing
for (String str : c)
{
System.out.println(str);
}
}
}
Output:
Hyderabad
Goa
Mumbai
Arrays.toString() function in Java:
Arrays.toString() is a static method of the Arrays class, which is part of the java.util package. It includes several techniques for manipulating arrays.
Syntax:
public static String toStr(int[] b)
As an argument, it takes an array of any primitive type. It produces a datatype of an array with a list of the array's elements. String.valueOf(int) is used to convert array elements to String.
Using Java toString() method:
PrintArrExample.java
import java.util.Arrays;
public class PrintArrExample
{
public static void main(String[] args)
{
//declaration and initialization of an array
int arr[] = {4,-1, 5, -19, 3};
//representating the array and returning the value
System.out.println(Arrays.toStr(arr));
}
}
Output:
[4, -1, 5, -19, 3]
Using Arrays deepToString() function:
The deepToString() function of the Java Arrays class converts multidimensional arrays to strings.
Syntax:
public static String deepToStr(Obj[] b)
As an argument, it accepts an array. It returns the array's String representation.
Using deepToString() method:
In the following example, we generated a two-dimensional float array.
import java.util.Arrays;
public class PrintArrExample
{
public static void main(String[] args)
{
//declaring and initializating of 2-D array of data type called float
float[][] arr= {{11.2f, 2.6f}, {4.9f, 4.2f}, {5.0f, 2.2f}};
System.out.println(Arrays.deepToStr(arr));
}
}
Output:
[[11.2, 2.6], [4.9, 4.2], [5.0, 2.2]]
Arrays.asList() function in Java:
Java Arrays.asList() is a static method of the java.util package's Java Arrays class. It serves as a link between array-based and collection-based APIs.
Syntax:
public static <L> List<L>asList(L...b)
The method also makes it simple to generate a fixed-size list with a large number of elements.
obj=Arrays.toStr(arr[] b) ListL>
As an argument, it takes an array. It returns the array's list view.
Using asList() method:
PrintArrExample.java
import java.util.Arrays;
public class PrintArrExample
{
public static void main(String [] args)
{
String[] stringArray={"Hi","Sahi"};
System.out.println(Arrays.asList(stringArr));
}
Output:
[Hi, Sahi]
Iterator interface in Java:
The Java Iterator interface is part of the java.util package. Iterator objects are generated by invoking the iterator() function. It is available in the Collection interface. It gives back an iterator.
Iterator interface illustration:
In the following example, we declare an array and populate it with elements. We first transform the supplied array to a list using the Arrays.asList() function since iterator allows us to traverse the collection and then use the collection class's iterator() method.
PrintArrExample.java
import java.util.Arrays;
import java.util.Iterator;
public class PrintArrExample
{
public static void main(String[] args)
{
Double[] arr = { 2.5, 4.6, 3.2, 4.1, 2.9};
Iterator<Double> it = Arrays.asList(arr).itr();
while(itr.hasN()){
System.out.println(itr.n());
}
}
}
Output:
2.5
4.6
3.2
4.1
2.9
The Java Stream API
A Java Stream is a data structure that can be computed on the fly. It does not keep any data. It works with the source data structure, such as a collection or an array. Internal iteration is implemented using the Java stream API. It has various characteristics, including sequential and parallel execution.
Java stream() function:
Java stream() is a static function of the java.util package's Java Arrays class. It is used to obtain an array's sequential stream.
Syntax:
public static <t>Stream stream(t[] arr)
Where t is the array type. The method takes an array of elements to convert into a sequential stream. It returns a sequential IntStream whose source is the supplied array.
Java forEach() function:
It's a final operation. It does not ensure that the encounter sequence of the stream will be respected.
Syntax:
void forEach(Consumer<? super t> action)
As an argument, the method accepts an action. Each element is subjected to non-interfering action. It produces no results.To print an array from a stream, we can use one of two terminal procedures.
stream.forEach() function example:
We used a different method to print an array in the following example. The forEach() method is used to loop through all of the stream's elements. The Iterable and Stream interfaces define it.
We utilised System.out, which is a reference to an object, within the forEach() method. It is a standard output stream. It includes a method named println (). It is an overloaded method that can accept any parameter. When we place the println() method behind the member access operator (::), it transforms into an expression.
PrintArrExample.java
import java.util.Arrays;
public class PrintArrExample
{
public static void main(String[] args)
{
String[] array= {"C", "C++", "Python"};
Arrays.str(array).forEach(System.out::println);
}
}
Output:
C
C++
Python