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How to Convert Int to String in Java?

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Java allows you to convert values from one data type to another, under certain conditions. You can convert a string variable to a numeric value and a numeric value into a string variable. In this article, let’s check out how to convert int to String in Java.

Listed below are different ways to convert int to string in Java:

For each of these methods, I will be discussing the syntax, parameters involved and return value along with sample example programs in Java. Let’s get started.

Converting int to string using Integer.toString(int)

The Integer class has a static method which returns a String object representing the int parameter specified in the Integer.toString(int) function. This approach, unlike the others, can return a NullPointerException.

Syntax

There are two different expressions for Integer.toString() method:

  • public static String toString(int i)
  • public static String toString(int i, int radix)

Parameters

The parameters of this method are:

  • i: the integer to be converted.
  • radix: the used base – number system in order to represent the string.

The radix value is an optional parameter and if it is not set, for the decimal base system the default value is 10. 

Return Value

The returned value for both expressions is a Java String that represents the integer “i” argument. If the radix parameter is used, the returned string is specified by the respective radix.

Convert Integer to String using Integer.toString().

package MyPackage;
public class Method1 
{
	public static void main(String args[]) 
	{
		  int n = Integer.MAX_VALUE;
		  String str1 = Integer.toString(n);
		  System.out.println("The output string is: " + str1);
		  int m = Integer.MIN_VALUE;
		  String str2 = Integer.toString(m);
		  System.out.println("The output string is: " + str2);
	}
	 
}

Output

The output string is: 2147483647
The output string is: -2147483648

Converting int to string using String.valueOf(int)

String.valueOf() is static utility method of String class that can convert most primitive data types to their String representation. It includes integers. This approach is considered as a best practice due to its simplicity.

Syntax

It is expressed as:

  • public static String valueOf(int i)

Parameter

  • i: the integer that needs to be converted 

Return Value

This method returns the string representation of the int argument.

Convert Integer to String using String.valueOf().

class Method2
{ 
  public static void main(String args[]) 
  { 
    int number = 1234; 
    String str = String.valueOf(number);
    System.out.println("With valueOf method: string5 = " + str);
  } 
}  

Output

With valueOf method: string5 = 1234

Converting int to String using String.format()

In Java, String.format() is a new alternative method that can be used for converting an Integer to a String object. Though the purpose of this method is to format a string, it can also be used for conversion.

Syntax

There are two different expressions:

  • public static String format(Locale l, String format, Object… args)
  • public static String format(String format, Object… args)

Parameters

The arguments for this method are:

  • l: the local to be addressed during the formatting
  • format: the format string, which includes format specifier and sometimes a fixed text
  • args: arguments that refer to the format specifiers set in the format parameter

Return Value

This method returns a formatted string, according to the format specifier and the specified arguments. 

Convert int to String using String.format().

class Method3
{ 
  public static void main(String args[]) 
  { 
    int number = -1234; 
    String str = String.format("%d", number);
    System.out.println("With format method: string = " + str);
  } 
}

Output

With format method: string = -1234

Converting int to String using DecimalFormat

DecimalFormat is a concrete subclass of NumberFormat class that formats decimal numbers. It has a lot of features designed to parse and format numbers. You can use it to format a number to a String representation following a certain pattern. Here’s an example program.

import java.text.DecimalFormat;
public class Method4
{
	 public static void main(String[] args) 
	 {
	      int number = 12345;
	      DecimalFormat numberFormat = new DecimalFormat("##,###");
	      String str = numberFormat.format(12345);	      
          System.out.println("The number to be converted is: " + number);
	      System.out.println("The string version of 12345 is: " + str);
	 }
	 
}

Output

The number to be converted is: 12345
The string version of 12345 is: 12,345

If you know how to use DecimalFormat method, it is the best option for converting Integer to String, because of the level of control that you can have with the formatting. You can specify the number of decimal places and comma separator for better readability as shown in the above example.

Converting int to String using StringBuffer or StringBuilder

StringBuilder and StringBuffer are the classes used to concatenate multiple values into a single String. StringBuffer is thread safe but slower, whereas StringBuilder isn’t thread safe but is faster. Below I have given an example demonstrating these classes and explained how it works. Take a look.

Convert int to String using StringBuilder/StringBuffer.

class Method5
{
  public static void main(String args[]) 
  { 
    int number1 = -1234;
    StringBuilder sb = new StringBuilder(); 
    sb.append(number1); 
    String str1 = sb.toString(); 
    System.out.println("With StringBuilder method: string = " + str1); 
    StringBuffer SB = new StringBuffer(); 
    SB.append(number1); 
    String str2 = SB.toString(); 
    System.out.println("With StringBuffer method: string = " + str2); 
  } 
} 

Output

With StringBuilder method: string = -1234
With StringBuffer method: string = -1234

The StringBuilder object represents a String object that can be modified and treated as an array with a sequence of characters. To add a new argument to the end of the string, StringBuilder instance implements the append() method. At the end it is important to call the toString() method, in order to take the string representation of the data. Alternatively, you can use the shorthand version of these classes as well. Here’s how to convert int to String in Java:

Example of converting int to String using StringBuilder/StringBuffer.

class Method6
{
  public static void main(String args[]) 
  { 
	String str1 = new StringBuilder().append(1234).toString(); 
    System.out.println("With StringBuilder method: string = " + str1); 
    String str2 = new StringBuffer().append(1234).toString(); 
    System.out.println("With StringBuffer method: string = " + str2); 
  } 
} 

Output

With StringBuilder method: string = -1234
With StringBuffer method: string = -1234

The most important thing is to call the toString() method, in order to get the string representation of the data.

This brings us to the end of this ‘How to Convert int to String in Java’ article. I have covered one of the fundamental topics of Java, converting an int or Integer to a String using tools shipped with the JDK. Hope you are clear with all that has been shared with you in this article.

Make sure you practice as much as possible and revert your experience.  

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