Converting Numbers to Strings in Java

Sometimes you need to convert a number to a string because you need to operate on the value in its string form. There are several easy ways to convert a number to a string:

 

Concatenate number with an empty string

For example:

int i=10;

// Concatenate i with an empty string "".

String s1 = "" + i;

Now string s1 contains the value "10".

Use the static valueOf() method in String class

String class provides the following overloaded static valueOf() methods to construct the string representation of the primitive types.

        public static String valueOf(char c)
        public static String valueOf(boolean b)
        public static String valueOf(int i)
        public static String valueOf(long l)
        public static String valueOf(float f)
        public static String valueOf(double d)

For example:
        String bool = String.valueOf(false);
        String ch = String.valueOf('c');
        String i = String.valueOf(10);
        String l = String.valueOf(100L);
        String f = String.valueOf(3.14f);
        String d = String.valueOf(3.14);

Use Wrapper classes Static toString() method

To convert a primitive type to a string you can use the following methods offered by the wrapper classes.

 

Wrapper	Static toString() method
Byte	toString(byte value)
Short	toString(short value)
Integer	toString(int value) toString(int value, int radix)
Long	toString(long value) toString(long value, int radix)
Float	toString(float value)
Double	toString(double value)
Character	toString(char c)
Boolean	toString(boolean b)
Void	None

For example:

 

        String b = Byte.toString((byte) 5);

        String s = Short.toString((short) 25);

        String i1 = Integer.toString(100);
        String i2 = Integer.toString(100, 2);

        String l1 = Long.toString(1000);
        String l2 = Long.toString(1000, 8);

        String f = Float.toString(3.14f);

        String d = Double.toString(3.14);

        String bool = Boolean.toString(false);

        String ch = Character.toString('c');

Notice that Integer and Long toString() methods take an additional argument, int radix, which indicates in what base (for example binary, octal, or hexadecimal) the first argument is represented.

For example,

String i1 = Integer.toString(1001,2);

Here converts binary 1001 to the corresponding decimal value 9 and assigns the string form of 9 to variable i1.

toXxxString() method(Binary, Hexadecimal, Octal)

The Integer and Long wrapper classes let you convert numbers in base 10 to other bases. These conversion methods, toXxxString(), take an int or long, and return a String representation of the converted number.The toXxxString() methods offered by the wrapper classes are given below.

Wrapper	Static toXxxString() method
Integer	toHexString(int value) toOctalString(int value) toBinaryString(int value)
Long	toHexString(long value) toOctalString(long value) toBinaryString(long value)
Float	toHexString(float value)
Double	toHexString(float value)

 
For example:

public class Main {

    public static void main(String args[]) {

        String i_binary = Integer.toBinaryString(15);
        String i_octal = Integer.toOctalString(15);
        String i_hex = Integer.toHexString(15);

        System.out.println("15 in hex=" + i_hex);
        System.out.println("15 in octal=" + i_octal);
        System.out.println("15 in binary=" + i_binary);

        String l_hex = Long.toHexString(100);
        String l_octal = Long.toOctalString(100);
        String l_binary = Long.toBinaryString(100);

        System.out.println("100 in hex=" + l_hex);
        System.out.println("100 in octal=" + l_octal);
        System.out.println("100 in binary=" + l_binary);

        String f_hex = Float.toHexString(3.14f);
        String d_hex = Double.toHexString(3.14);

        System.out.println("3.14f in hex=" + f_hex);
        System.out.println("3.14 in hex=" + d_hex);

    }

}

The output is

15 in hex=f
15 in octal=17
15 in binary=1111
100 in hex=64
100 in octal=144
100 in binary=1100100
3.14f in hex=0x1.91eb86p1
3.14 in hex=0x1.91eb851eb851fp1