The challenge
We need a function that can transform a string into a number. What ways of achieving this do you know?
Note: Don’t worry, all inputs will be strings, and every string is a perfectly valid representation of an integral number.
Examples
stringToNumber("1234") == 1234
stringToNumber("605" ) == 605
stringToNumber("1405") == 1405
stringToNumber("-7" ) == -7
Test cases
import org.junit.Test;
import static org.junit.Assert.assertEquals;
public class StringToNumberTest {
@Test
public void test1(){
assertEquals("stringToNumber(1234)", 1234 , StringToNumber.stringToNumber("1234"));
}
@Test
public void test2(){
assertEquals("stringToNumber(605)", 605 , StringToNumber.stringToNumber("605"));
}
@Test
public void test3(){
assertEquals("stringToNumber(1405)", 1405 , StringToNumber.stringToNumber("1405"));
}
@Test
public void test4(){
assertEquals("stringToNumber(-7)", -7 , StringToNumber.stringToNumber("-7"));
}
@Test
public void test5(){
for(int i = 0; i < 100; ++i) {
int t = (int)Math.round(Math.random() * 500000);
assertEquals("stringToNumber(" + t + ")", t , StringToNumber.stringToNumber(Integer.toString(t)));
}
}
}
The solution in Java
Option 1 (using parseInt):
public class StringToNumber {
public static int stringToNumber(String str) {
return Integer.parseInt(str);
}
}
Option 2 (using valueOf):
public class StringToNumber {
public static int stringToNumber(String str) {
return Integer.valueOf(str);
}
}
It may be good practice to go a step further and sanity check the output:
public class StringToNumber {
public static int stringToNumber(String str) {
try {
return Integer.parseInt(str);
} catch (NumberFormatException NFE) {
throw NFE;
}
}
}