Different Ways For Integer to String Conversions in Java

We generally counter with such conversion articles because many operations can be performed over a string while we are limited to when it comes to integers. We have a wide varied list of in-built methods in the String class that helps us perform hassle-free operations. 

Suppose we are required to concatenate two integers then it would become a tedious job as we need to go through as we need to deal with the number system corresponding to which we will be playing mathematics within the number system. But in order to convert integer to string in Java, we have some inbuilt methods and classes which make out work too easy. 

Tip: We generally convert primitive class data members types though we have the concept of Wrapper classes to Strings because in practical programming in java we deal with strings.

Different Methods For Integer to String Conversions

1. Using toString() method of Integer class
2. Using valueOf() method of String class
3. Using Integer(int).toString() method of Integer class
4. Using DecimalFormat Class
5. Using StringBuffer class
6. using StringBuilder class 
7. Using special radix and custom radix
8. Using concatenation with an empty string  

1. Using toString Method of Integer Class

The Integer class has a static method toString() that returns a String object representing the specified int parameter. The argument is converted and returned as a string instance. If the number is negative, the sign will be preserved.

Example:

Java

// Java Program to Illustrate Integer to String Conversions
// Using toString() Method of Integer Class

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Custom input integers
        int a = 1234;
        int b = -1234;

        // Converting integer to string
        // using toString() method
        String str1 = Integer.toString(a);
        String str2 = Integer.toString(b);

        // Printing the above strings that
        // holds integer
        System.out.println("String str1 = " + str1);
        System.out.println("String str2 = " + str2);
    }
}

Output

String str1 = 1234
String str2 = -1234

2. Using valueOf() method of String Class

The String class has a static method valueOf() that can be used to convert the Integer to String as shown below:

Example 1:

Java

// Java Program to Illustrate Integer to String Conversions
// Using valueOf() Method of String class

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Custom integer input
        int c = 1234;

        // Converting above integer to string
        // using valueOf() Method
        String str3 = String.valueOf(c);

        // Printing the integer stored in above string
        System.out.println("String str3 = " + str3);
    }
}

Output

String str3 = 1234

Example 2:

Java

// Java Program to Illustrate Integer to String Conversions
// Using valueOf() Method of String class

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Passing input integer as in argument and
        // storing it in a string
        String str3 = String.valueOf(1234);

        // Printing the integer stored in above string
        System.out.println("String str3 = " + str3);
    }
}

Output

String str3 = 1234

3. Using toString() method of the Integer class

It is different from method 1 as proposed above, as in this method we use an instance of the Integer class to invoke its toString() method. 

Example 1:

Java

// Java Program to Illustrate
// Integer to String Conversions
// Using Integer(int).toString() Method

// Importing required classes
import java.util.*;

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Custom input integer
        int d = 1234;

        // Creating an object of Integer class
        // inside main() method
        Integer obj = new Integer(d);
        String str4 = obj.toString();

        // Printing the above string
        // holding integer value
        System.out.println("String str4 = " + str4);
    }
}

Output

Example 2:

Java

// Java Program to Illustrate
// Integer to String Conversions
// Using toString() Method of
// Integer Class

// Importing required classes
import java.util.*;

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Custom input integer
        int d = 1234;

        // Converting integer to string
        // using toString() method of Integer class
        String str4 = new Integer(d).toString();

        // Printing the integer value stored in above string
        System.out.println("String str4 = " + str4);
    }
}

Output

Example 3:

Java

// Java Program to Illustrate
// Integer to String Conversions
// Using toString() Method of
// Integer Class

// Importing required classes
import java.util.*;

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Passing integer inside object as soon it is
        // created via parameterised constructor and
        // converting integer to string using toString()
        // method and storing it into a String
        String str4 = new Integer(1234).toString();

        // Printing the above string holding integer value
        System.out.println("String str4 = " + str4);
    }
}

Output

Output explanation: If the variable is of primitive type (int), it is better to use Integer.toString(int) or String.valueOf(int). But if the variable is already an instance of Integer (wrapper class of the primitive type int), it is better to just invoke its toString() method as shown above. 

Note: This method is not efficient as an instance of the Integer class is created before conversion is performed.

4. Using DecimalFormat Class

DecimalFormat is a class that formats a number to a String. 

Example 1:

Java

// Java Program to Illustrate Integer to String Conversions
// Using DecimalFormat Class

// Importing required classes
import java.text.DecimalFormat;

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Custom integer input
        int e = 12345;

        // Creating an object of DecimalFormat class
        // inside main() method
        DecimalFormat df = new DecimalFormat("#");

        // Formatting the integer to string
        // and storing it in a string
        String str5 = df.format(e);

        // Printing the above stored value
        // inside a string
        System.out.println(str5);
    }
}

Output

12345

Example 2:

Java

// Java Program to Illustrate
// Integer to String Conversions
// Using DecimalFormat Class

// Importing required classes
import java.text.DecimalFormat;

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Input integer value
        int e = 12345;

        // Creating an object of DecimalFormat class
        // inside main() method
        DecimalFormat df = new DecimalFormat("#,###");

        // Converting above integral value to string
        String Str5 = df.format(e);

        // Printing the value stored in above string
        System.out.println(Str5);
    }
}

Output

Tip: Using this method, you can specify the number of decimal places and comma separator for readability.

5. Using StringBuffer class 

StringBuffer is a class that is used to concatenate multiple values into a String. 

Example 1:

Java

// Java Program to Illustrate
// Integer to String Conversions
// Using StringBuffer Class

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Integer input value
        int f = 1234;

        // Creating an object of StringBuffer class
        StringBuffer sb = new StringBuffer();
        sb.append(f);

        String str6 = sb.toString();

        System.out.println("String str6 = " + str6);
    }
}

Output

String str6 = 1234

Example 2:

Java

// Java Program to Illustrate
// Integer to String Conversions
// Using StringBuffer Class

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        String str6
            = new StringBuffer().append(1234).toString();

        System.out.println("String str6 = " + str6);
    }
}

Output

String str6 = 1234

Output: 

String str6 = 1234

6. Using StringBuilder Class

StringBuilder works similarly but is not thread-safe like StringBuffer. 

Example 1:

Java

// Java Program to Illustrate
// Integer to String Conversions
// Using StringBuilder Class

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Input integer
        int g = 1234;

        // Creating an object of StringBuilder class
        // inside main() method
        StringBuilder sb = new StringBuilder();
        sb.append(g);

        String str7 = sb.toString();

        // Printing the value stored in above string
        System.out.println("String str7 = " + str7);
    }
}

Output

String str7 = 1234

Example 2:

Java

// Java Program to Illustrate Different Ways for
// Integer to String Conversions
// Using StringBuilder Class

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        String str7
            = new StringBuilder().append(1234).toString();

        // Printing the value stored in above string
        System.out.println("String str7 = " + str7);
    }
}

Output

String str7 = 1234

Note: All the examples above use the base (radix) 10. Following are convenient methods to convert to binary, octal, and hexadecimal systems. The arbitrary custom number system is also supported. 

7A. Using special radix 

Example: Binary

Java

// Java Program to Illustrate Integer to String Conversions
// Using Special Radix In Binary Numbers

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Input integer
        int h = 255;
        String binaryString = Integer.toBinaryString(h);

        // Printing the binary number stored in above string
        System.out.println(binaryString);
    }
}

Output

11111111

Output Explanation: 11111111 is the binary representation of the number 255.

Example: Octal 

Java

// Java Program to Illustrate Integer to String Conversions
// Using Special Radix In Octal Numbers

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Custom input integer
        int i = 255;
        String octalString = Integer.toOctalString(i);

        // Printing the octal number stored in above string
        System.out.println(octalString);
    }
}

Output

377

377 is the octal representation of the number 255. 

Example: Hexadecimal 

Java

// Java Program to Illustrate Integer to String Conversions
// Using Special Radix In Hexadecimal Numbers

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Custom input integer
        int j = 255;
        String hexString = Integer.toHexString(j);

        // Printing the hexadecimal number
        // stored in above string
        System.out.println(hexString);
    }
}

Output

ff

The ff is the hexadecimal representation of the number 255.

7B. Custom Base/Radix 

Approach: We are using the toString() method of the Integer class to get it converted into a string where additionally we will be passing a value as an argument known as radix. One can use any other custom base/radix when converting an int to string. In the below example, for illustration purposes, we are considering the base 7 number system. 

Example:

Java

// Java Program to Illustrate Integer to String Conversions
// Using Custom Radix

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Input integer value
        int k = 255;

        // Setting base as 7, converting integer to string
        // using toString() method and
        // storing it into a string
        String customString = Integer.toString(k, 7);

        // Printing value stored in above string
        System.out.println(customString);
    }
}

Output

Note: 513 is the representation of the number 255 when written in the base 7 system.

8. Using concatenation with an empty string

Approach: Here we will declare an empty string and using the ‘+’ operator, we will simply store the resultant as a string. Now by virtue of this, we are successfully able to append and concatenate these strings. 

Example:

Java

// Java Program to Illustrate Integer to String Conversions
// Using Concatenation with Empty String

// Main class
class GFG {

    // Main driver method
    public static void main(String args[])
    {
        // Custom integer values
        int a = 1234;
        int b = -1234;

        // Concatenating with empty strings
        String str1 = "" + a;
        String str2 = "" + b;

        // Printing the concatenated strings
        System.out.println("String str1 = " + str1);
        System.out.println("String str2 = " + str2);
    }
}

Output

String str1 = 1234
String str2 = -1234

This article is contributed by Amit Khandelwal. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.