What is the method to check whether a character is a letter or digit?

1. isDigit(char)
2. isLetterOrDigit()
3. isLetterOrDigit(char)
4. isLETTERorDIGIT(char)

The method to convert a String to double is:

1. String.toDouble()
2. Double.Parsedouble()
3. Double.parseDouble(String)
4. Double.parseDouble()

String s1 = "45.50"; String s2 = "54.50";
double d1=Double.parseDouble(s1);
double d2=Double.parseDouble(s2);
int x= (int)(d1+d2);

What is value of x?