Java Convert int to String - Different Ways of Conversion

Converting an int to a String is an important type conversion. Many operations can be performed over a string, while we are limited when it comes to integers. We have a wide varied list of in-built methods in the String class that help us perform hassle-free operations. 

Suppose we are required to concatenate two integers then it would become a tedious for us. 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 to convert integers to strings in Java, we have some inbuilt methods and classes which make our 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.

Ways to Convert int to a String in Java

Converting Integers to Strings involves using the Integer classes toString() or String.valueOf() for direct conversion. String.format() is another method offering flexible formatting options. Using StringBuilder or StringBuffer for appending integer values as strings is efficient for extensive string manipulation.

There are certain methods for Integer to String conversions mentioned below:

1. Using the toString() method of the Integer class
2. Using the valueOf() method of the String class
3. Using Integer(int).toString() method of Integer class
4. 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:

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:

String str3 = 1234

3. Using Integer(int).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:

String str4 = 1234

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. And deprecated and marked as removal.

4. Using Concatenation with an Empty String

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

Example:

String str1 = 1234
String str2 = -1234

Advanced Methods to Convert int to String

There are certain advance Methods are mentioned below:

1. Using DecimalFormat Class
2. Using StringBuffer class
3. using StringBuilder class 
4. Using special radix and custom radix

1. Using DecimalFormat Class

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

Example:

12,345

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

2. Using StringBuffer Class 

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

Example 1:

String str6 = 1234

Example 2:

String str6 = 1234

3. Using StringBuilder Class

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

Example 1:

String str7 = 1234

Example 2:

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. 

Converting int to String With Different Base

We can also convert int to String in different bases below are the some of the important methods are mentioned which help to convert int to String with different base.

1. Using Special Radix 

Example 1: Converting int(base 2 or binary number) to String using Integer class method toBinary().

11111111

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

Example 2: Converting int(base 8 or octal number) to String using Integer class method toOctalString().

377

Explanation: 377 is the octal representation of the number 255. 

Example 3: Converting int(base 10 or Hexadecimal number) to String using Integer class method toHexString().

ff

Explanation: The ff is the hexadecimal representation of the number 255.

2. 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 a string. In the example below, we are considering the base 7 number system for illustration purposes. 

Example: Converting int(base 7 or custom radix number) to String using Integer class method toString(int I, int radix).

513

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