Convert string number to integer number

Question

I have "1" as a string, and I would like to convert it to decimal, 1, as integer.

I tried charAt(), but it returns 49, not 1 integer.

So, what is required to convert the "1" string to 1 integer?

`49` is the numerical equivalent for the character `1`. To get the numerical value of a single character, you can do this: `c - '0'`. So, `'1' - '0' = 1`. — Obicere, Sep 30 '13 at 20:19
@Obicere - Yep, while that's almost certainly not what the OP wanted, it's worthwhile to point it out. An important step in understanding the difference between a (conceptual) number and it's physical representation. — Hot Licks, Sep 30 '13 at 20:24
@HotLicks it will be extremely useful if he wishes to create his own method for parsing it. — Obicere, Sep 30 '13 at 20:27
@Obicere - Yes, especially if his instructor assigns him the task of writing a number parser from scratch. (And it seems to be a popular assignment, and one that many folks break their pick on.) — Hot Licks, Sep 30 '13 at 20:33

KhAn SaAb · Accepted Answer · 2018-07-20T09:45:31.160

28

Use Wrapper Class.

Examples are below

int

int a = Integer.parseInt("1"); // Outputs 1

float

float a = Float.parseFloat("1"); // Outputs 1.0

double

double a = Double.parseDouble("1"); // Outputs 1.0

long

long a = Long.parseLong("1"); // Outputs 1

edited Jul 20 '18 at 09:45

answered Sep 30 '13 at 20:20

KhAn SaAb

1

Or Float, or Double, depending on the type of data. – Hot Licks Sep 30 '13 at 20:22

score 8 · Answer 2 · answered Sep 30 '13 at 20:20

8

int one = Integer.parseInt("1");

Ideally you should be catching errors too:

int i;
String s = "might not be a number";
try {
   i = Integer.parseInt(s);
} catch (NumberFormatException e) {
   //do something
}

answered Sep 30 '13 at 20:20

Moob

score 6 · Answer 3 · answered Sep 30 '13 at 20:20

6

Integer.parseInt does exactly that.

int foo = Integer.parseInt("1");

answered Sep 30 '13 at 20:20

federico-t

score 4 · Answer 4 · edited Sep 30 '13 at 20:21

4

int foo = Integer.parseInt("1");
//foo now equals 1

edited Sep 30 '13 at 20:21

Arup Rakshit

answered Sep 30 '13 at 20:21

user446836

score 2 · Answer 5 · answered Sep 30 '13 at 20:21

2

String s = "1";
int i = Integer.valueOf(s);

answered Sep 30 '13 at 20:21

Mureinik

5 Answers5