How do you turn the first (numerical) character of a string into an integer in Java?

Question

So let's say I have a double which is 1.5, and then I convert it to a string, then try to turn the first character into a string using the char.at method.

double a = 1.5;
String b = String.valueOf(a);
System.out.println(Integer.valueOf(b.charAt(0)));

But when I did that, here's the output I received:

49

What did I do wrong?

Answer 1

valueOf takes either an int or a String. You passed a char (returned by charAt) which got promoted to an integer. You can use substring to get the first character of the string instead.

double a = 1.5;
String b = String.valueOf(a);
System.out.println(Integer.valueOf(b.substring(0, 1)));

Answer 2

It's taking the ascii value of the first character.

If you want to pass Integer.valueOf a String as a parameter, try the following:

double a = 1.5;
String b = String.valueOf(a);
System.out.println(Integer.valueOf(Character.toString(b.charAt(0))));

Also, if you want to pass an integer, Integer.valueOf can also be used as following:

double a = 1.5;
String b = String.valueOf(a);
System.out.println(Integer.valueOf(Character.getNumericValue(b.charAt(0))));

Output:

1

Answer 3

Just use Character.getNumericValue(b.charAt(0)); to get actual value instead of ASCII

Answer 4

There are various methods to do this, one is the following (using the Double class):

Double number = 1.5;
System.out.println(number.intValue());

The intValue() method will return the int representation of the istance of Double