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)

Differentiate between boxing and unboxing.

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?

Assertion (A): Integer class can be used in the program without calling a package.

Reason (R): It belongs to the default package java.lang.

1. Both Assertion (A) and Reason (R) are true and Reason (R) is a correct explanation of Assertion (A)
2. Both Assertion (A) and Reason (R) are true and Reason (R) is not a correct explanation of Assertion(A)
3. Assertion (A) is true and Reason (R) is false
4. Assertion (A) is false and Reason (R) is true