Thursday, December 27, 2012

3 Example to print array values in Java - toString and deepToString from Arrays

Printing array values in Java or values of array element in Java would have been much easier if  arrays are allowed to directly prints its values whenever used inside System.out.println() or format and printf method, Similar to various classes in Java do this by overriding toString() method. Despite being an object, array in Java doesn't print any meaningful representation of its content when passed to System.out.println() or any other print methods. If you are using array in method argument or any other prominent place in code and actually interested in values of array then you don't have much choice than for loop until Java 1.4. Things has been changed since Java 5 because it introduced two extremely convenient methods for printing values of both primitive and object arrays in Java. Arrays.toString(array) and Arrays.deepToString(twoDimensionArray) can print values of any array. Main difference between Arrays.toString() and Arrays.deepToString  is that deepToString is used to print values of multidimensional array which is far more convenient than nesting of multiple for loops. In this Java tutorial we will see 3 different ways of printing array values in Java or value of element from Array in Java.

3 ways to print array values in Java

As I said there is no direct way to print values of array in Java if you directly pass primitive or object array to System.out.println() you will receive following output:

System.out.println("Print array values in Java 1.4 :" + Arrays.asList(sArray));
System.out.println("Print array values in Java 1.4 :" + Arrays.asList(iArray));

Output:
Printing Integer array in Java: [I@15b7986
Printing String array in Java: [Ljava.lang.String;@87816d

You can't decipher anything until you are quite familiar of this array format and even then it doesn't tell anything about contents of array. It just print type of element and hashcode. In order to print values of array you can use any of following 3 examples:

1) Use enhanced for loop or classic for loop with lenth of array.
2) Use Arrays.asList() to convert Array into ArrayList and than print
3) Use Java 5 Arrays.toString() and Arrays.deepToString() methods

Print Array Value Example 1: Using for loop

How to print values of Array or values of elements from Array in Javafor loop is the classical way of printing or displaying values of both one dimension and multidimensional arrays in Java. before Java 5 you can use array.length to iterate over all array elements and printing values for each of them. From Java 5 onwards you can use much cleaner enhanced for loop which doesn't require any counter from moving one element to other in Java. Enhanced for loop in Java 5 is added with other popular language feature e.g. Enum, Autoboxing and Generics. Here is sample code example to print value of element from array using classical and enhanced for loop in Java:

// Classic for loop before Java 5
private static int[] iArray = new int[]{1, 2,3,4, 5};

for(int i=0; i< iArray.length; i++){
   System.out.print(iArray[i] +", ");
}

Output:
1, 2, 3, 4, 5,

//Enhanced for loop from Java 1.5
for(int i : iArray){
   System.out.print(i +", ");
}

As you see using enhanced for loop for printing array values is more concise and clean.

Print Array Values Example 2: Using Arrays.asList

Arrays.asList() method is used to convert Array into ArrayList and as you know Collection classes overrides toString method to print there contents. By converting array into List we can leverage that property and print values from ArrayList instead of Array. Only limitation of this approach is it doesn't print contents of array if array is of primitive type like int, float or double but works well if Array contains objects like String. Arrays.asList() is also used to create and initialize List in one line. By the way here is simple code example of displaying values form array in Java using Arrays.asList() method:

System.out.println("Print String array values in Java 1.4 :" + Arrays.asList(sArray));
System.out.println("Print int array values in Java 1.4 :" + Arrays.asList(iArray));

Output:
Print String array values in Java 1.4 :[abc, bcd, def, efg]
Print int array values in Java 1.4 :[[I@15b7986]

Print Array Value Example 3: using Arrays.toString and Arrays.deepToString

This is by far best and recommended way of printing values from Array in Java. Only caveat is that Arrays.toString() and Arrays.deepToString() are added from Java 5 onwards along with other features e.g. Generics, varargs or static import. Use Arrays.toString() method to print both primitive and object single or one dimension array and use Arrays.deepToString() method to print values from two dimensional or multidimensional array (array of array in Java). Here is a simple example of printing array values using Arrays.toString() and Arrays.deepToString() in Java:

System.out.println("Print values of Integer array in Java: " + Arrays.toString(iArray));
System.out.println("Print values of String array in Java: " + Arrays.toString(sArray));
     
int[][] twoDimensionArray = new int[][]{
                                    {1,2,3},
                                    {10,20,30},
                                    {100,200,300},
                                    };
System.out.println("Print two dimensional array in Java: " + Arrays.deepToString(twoDimensionArray));

Output:
Print values of Integer array in Java: [1, 2, 3, 4, 5]
Print values of String array in Java: [abc, bcd, def, efg]
Print two dimensional array in Java: [[1, 2, 3], [10, 20, 30], [100, 200, 300]]

Java program to print array values

Here is the combined examples of printing value of elements from Array in Java using above three examples. Best way to print elements of Array is to use new methods added in java.util.Arrays class in Java 5 e.g. toString() and deepToString().

import java.util.Arrays;

public class PrintArrayExample {

    private static int[] intArray = new int[]{1, 2,3,4, 5};
    private static String[] strArray = new String[]{"abc", "bcd", "def", "efg"};
   
    public static void main(String args[]) {
        System.out.println("Java Example to print int array in Java: " + intArray);
        System.out.println("Java Example to print string array in Java: " + strArray);
     
        //generic way of printing values of array before java 5      
        for(int i=0; i< intArray.length; i++){
            System.out.print(intArray[i] +", ");
        }
     
        //printing array values using enhanced for loop java 1.5
        for(int i : intArray){
            System.out.print(i +", ");
        }
     
        //another way to print array values in Java 1.4 is using Arrays.asList
        System.out.println("Java Example to print String array values in Java 1.4 :"
                            + Arrays.asList(strArray));
        System.out.println("Java Example to int array values in Java 1.4 :"
                            + Arrays.asList(intArray));
     
        //better way of printing values of array in java 1.5      
        System.out.println("Java Example to print values of array in Java: "
                            + Arrays.toString(intArray));
        System.out.println("Java Example to print values of array in Java: "
                            + Arrays.toString(strArray));
     
        int[][] twoDimensionArray = new int[][]{
                                    {1,2,3},
                                    {10,20,30},
                                    {100,200,300},
                                    };
        System.out.println("Java Example to print two dimensional array in Java: "
                            + Arrays.deepToString(twoDimensionArray));

    }
}

Output:
Java Example to print int array in Java: [I@1820dda
Java Example to print string array in Java: [Ljava.lang.String;@15b7986
1, 2, 3, 4, 5, 1, 2, 3, 4, 5, Java Example to print String array values in Java 1.4 :[abc, bcd, def, efg]
Java Example to int array values in Java 1.4 :[[I@1820dda]
Java Example to print values of array in Java: [1, 2, 3, 4, 5]
Java Example to print values of array in Java: [abc, bcd, def, efg]
Java Example to print two dimensional array in Java: [[1, 2, 3], [10, 20, 30], [100, 200, 300]]

That's all on how to print array values in Java. we have seen three different example to display contents of array in Java and most easy and convenient approach is using Arrays.toString() and Arrays.deepToString(). if you are using Java 5.

Related Java Collection tutorials from Javarevisited Blog

3 comments :

Anonymous said...

I was looking for any easy to print array in Java, didn't know about toString() method of Arrays class. This post gives me lot of insight on How to print array in Java but same time I think Why not use ArrayList in place of array?

Anonymous said...

How to print primitive array in Java 1.4, As I see toString and deppToString of Arrays class is only available post Java 5.

Anonymous said...

Hi, is there anyone who can help me doing a java programming task?

currently I'm trying to create a task named Tarski's World...
It's a program where you make row and column ( 10x10 ) and then inside the empty array spaces it will generate type of objects with attributes colours and shapes of the objects randomly. ( such as; blue square, red square, red rectangle, green rectangle) .

The generated object n colour will fill all the columns and rows...

I had tried few coding that referring to the internet... but none of it is working properly... need help from you guys...

thanks...

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