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Different ways for Integer to String Conversions In Java
  • Difficulty Level : Easy
  • Last Updated : 01 May, 2021
  • Convert using Integer.toString(int) 
    The Integer class has a static method that returns a String object representing the specified int parameter. 
    Syntax :
public static String toString(int i)

The argument i is converted and returned as a string instance. If the number is negative, the sign will be preserved. 

Example : 

Java




class GfG
{
  public static void main(String args[])
  {
    int a = 1234;
    int b = -1234;
    String str1 = Integer.toString(a);
    String str2 = Integer.toString(b);
    System.out.println("String str1 = " + str1);
    System.out.println("String str2 = " + str2);
  }
}

Output: 

String str1 = 1234
String str2 = -1234

Java




class GfG
{
  public static void main(String args[])
  {
    int c = 1234;
    String str3 = String.valueOf(c);
    System.out.println("String str3 = " + str3);
  }
}

or 

Java




class GfG
{
  public static void main(String args[])
  {
    String str3 = String.valueOf(1234);
    System.out.println("String str3 = " + str3);
  }
}

Output: 



String str3 = 1234
  • Convert using Integer(int).toString() 
    This method uses an instance of the Integer class to invoke its toString() method. 
    Example : 

Java




class GfG
{
  public static void main(String args[])
  {
    int d = 1234;
    Integer obj = new Integer(d);
    String str4 = obj.toString();
    System.out.println("String str4 = " + str4);
  }
}

or 

Java




class GfG
{
  public static void main(String args[])
  {
    int d = 1234;
    String str4 = new Integer(d).toString();
    System.out.println("String str4 = " + str4);
  }
}

or 

Java




class GfG
{
  public static void main(String args[])
  {
    String str4 = new Integer(1234).toString();
    System.out.println("String str4 = " + str4);
  }
}

Output: 

String str4 = 1234

If your variable is of primitive type (int), it is better to use Integer.toString(int) or String.valueOf(int). But if your 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. 
This method is not efficient as an instance of Integer class is created before conversion is performed.

  • Convert using DecimalFormat 
    The class java.text.DecimalFormat is a class that formats a number to a String. 
    Example :

Java




import java.text.DecimalFormat;
class GfG
{
  public static void main(String args[])
  {
    int e = 12345;
    DecimalFormat df = new DecimalFormat("#");
    String str5 = df.format(e);
    System.out.println(str5);
  }
}

Output: 

String str5 = 12345

or 

Java




import java.text.DecimalFormat;
class GfG
{
  public static void main(String args[])
  {
    int e = 12345;
    DecimalFormat df = new DecimalFormat("#,###");
    String Str5 = df.format(e);
    System.out.println(Str5);
  }
}

Output: 

String str5 = 12,345

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



  • Convert using StringBuffer or StringBuilder 
    StringBuffer is a class that is used to concatenate multiple values into a String. StringBuilder works similarly but not thread-safe like StringBuffer. 
    StringBuffer Example 

Java




class GfG
{
  public static void main(String args[])
  {
    int f = 1234;
    StringBuffer sb = new StringBuffer();
    sb.append(f);
    String str6 = sb.toString();
    System.out.println("String str6 = " + str6);
  }
}

or 

Java




class GfG
{
  public static void main(String args[])
  {
    String str6 = new StringBuffer().append(1234).toString();
    System.out.println("String str6 = " + str6);
  }
}

Output: 

String str6 = 1234
  • StringBuilder Example 

Java




class GfG
{
  public static void main(String args[])
  {
    int g = 1234;
    StringBuilder sb = new StringBuilder();
    sb.append(g);
    String str7 = sb.toString();
    System.out.println("String str7 = " + str7);
  }
}

or 

Java




class GfG
{
  public static void main(String args[])
  {
    String str7 = new StringBuilder().append(1234).toString();
    System.out.println("String str7 = " + str7);
  }
}

Output: 

String str7 = 1234
  • Convert with special radix 
    All the examples above use the base (radix) 10. Following are convenient methods to convert to binary, octal, and hexadecimal system. The arbitrary custom number system is also supported. 
    Examples :
    Binary

Java




class GfG
{
  public static void main(String args[])
  {
    int h = 255;
    String binaryString = Integer.toBinaryString(h);
    System.out.println(binaryString);
  }
}

Output: 

11111111

11111111 is the binary representation of the number 255.

Octal 

Java




class GfG
{
  public static void main(String args[])
  {
    int i = 255;
    String octalString = Integer.toOctalString(i);
    System.out.println(octalString);
  }
}

Output: 

377

377 is the octal representation of the number 255. 

Hexadecimal 

Java




class GfG
{
  public static void main(String args[])
  {
    int j = 255;
    String hexString = Integer.toHexString(j);
    System.out.println(hexString);
  }
}

Output: 

ff

The ff is the hexadecimal representation of the number 255.

Custom Base/Radix 
You can use any other custom base/radix when converting an int to String. 
The following example uses the base 7 number system. 

Java




class GfG
{
  public static void main(String args[])
  {
    int k = 255;
    String customString = Integer.toString(k, 7);
    System.out.println(customString);
  }
}

Output: 

513

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

Using concatenation with empty String :

Java




class GfG {
    public static void main(String args[])
    {
        int a = 1234;
        int b = -1234;
        String str1 = "" + a;
        String str2 = "" + b;
        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 contribute.geeksforgeeks.org or mail your article to contribute@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.
 

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