If the size of an int
(-2^31) isn't big enough you may need to consider using primitive type long
or Long
object when converting from a string. In this example we will show how to convert a string to a primitive double
, object Double
and vise versa. Just like when you change a string to an int you will need to handle NumberFormatException
in the instance your string has both numeric and characters. If you are stuck with a chars among digits you could use a regex to obtain all numerals.
String to primitive double
@Test
public void string_to_double_primitive() {
String myString = "2";
double variable = Double.parseDouble(myString);
assertEquals(2, variable, 0);
}
Primitive double to string
@Test
public void primitive_double_to_string() {
double number = 2;
assertEquals("2.0", String.valueOf(number));
}
StringBuffer to primitive double
@Test
public void stringbuffer_to_primitive_double() {
StringBuffer buffer = new StringBuffer("2");
assertEquals(2, Double.parseDouble(buffer.toString()), 0);
}
Stringbuilder to double
@Test
public void stringbuider_to_double() {
StringBuilder builder = new StringBuilder("2");
assertEquals(2, Double.parseDouble(builder.toString()), 0);
}
Double object to string
@Test
public void double_object_to_string() {
Double doubleToString = Double.valueOf("2");
assertEquals("2.0", doubleToString.toString());
}
String to double object
@Test
public void string_to_double_object() {
Double stringToDoubleObject = Double.parseDouble("2");
assertEquals(new Double(2), stringToDoubleObject);
}