In programming we will come across a situation where we need to convert number to string and string to number.
Converting Numbers to String:
There are many ways of converting numbers into string object,
- By concatenating number with empty string i.e.
" + "
operator
- The
valueOf()
method converts the given data type to String
.
- Each of the
Number
subclass includes a class method, toString
, that will convert its primitive type in to a String
.
Converting Numbers to String
class NumberstoStringTest
{
public static void main(String arg[])
{
int i = 32;
String s1 = "" + i; // LINE A
System.out.println("s1 = " + s1);
double d = 876.54;
String s2 = String.valueOf(d); // LINE B
System.out.println("s2 = " + s2);
float f = 156.8f;
String s3 = Float.toString(f); // LINE C
System.out.println("s3 = " + s3);
String s4 = "" + i + d; // LINE D
System.out.println("s4 = " + s4);
int n = s4.indexOf('.');
System.out.println(n + " Digits before decimal point of s4 string.");
System.out.println(s4.length() - n - 1
+ " Digits after decimal point of s4 string.");
}
}
OUTPUTs1 = 32
s2 = 876.54
s3 = 156.8
s4 = 32876.54
5 Digits before decimal point of s4 string.
2 Digits after decimal point of s4 string.
DESCRIPTIONIn this program, at LINE A
, int
is converted into String
by concatenating with empty string,
At LINE B
double
is converted into String
using valueOf
method,
At LINE C
float
is converted into String
using toString
method and finally at LINE D
, we are concatenating empty String, integer
and double
.
We are counting number of digits before and after the decimal point, in the resultant String.
THINGS TO TRY
- Apply
valueOf
method to different data types as String.valueOf(datatype)
.
- Apply
toString
method to all the data types as Integer.toString(integer_Datatype), Double.toString(double_datatype)
etc.,
- Try to perform operations on the resultant strings.
Converting Strings to Number:
The two ways of converting Strings into specified data type are,
- The
valueOf()
method converts the String
to specified data type.
- The parsing methods are widely used to convert strings into numbers.
Converting Strings to Number
class StringstoNumberTest
{
public static void main(String arg[])
{
String s1 = "25";
int i1 = Integer.valueOf(s1); // LINE E
int i2 = Integer.parseInt(s1); // LINE F
System.out.println(i1 + " " + i2);
float f1 = Float.valueOf(s1);
float f2 = Float.parseFloat(s1);
System.out.println(f1 + " " + f2);
double d1 = Double.valueOf(s1);
double d2 = Double.parseDouble(s1);
System.out.println(d1 + " " + d2);
System.out.print("The sum of all numbers is : ");
System.out.println(i1 + i2 + f1 + f2 + d1 + d2); // LINE G
String s2 = "ABCD";
char c1[] = new char[s2.length()];
for (int i = 0; i < s2.length(); i++) {
c1[i] = Character.valueOf(s2.charAt(i)); // LINE H
}
for (int j = 0; j < c1.length; j++) {
System.out.print(c1[j] + " ");
}
}
}
OUTPUT25 25
25.0 25.0
25.0 25.0
The sum of all numbers is : 150.0
A B C D
DESCRIPTIONIn this program, at LINE E
and LINE F
, string s1
is converted into integer by using valueOf
, parseInt
methods respectively. Similarly float
and double
are converted from string s1
. At LINE G
all 6 numbers sum is printed. At LINE H
the string s2
containing ABCD
is converted into character array and all characters are displayed.