JOptionPane is a class which has methods for doing input and output operations.
The method which you use for input is called showMessageDialog().
The statement
String s = JOptionPane.showInputDialog(
"Enter your first integer");
causes a dialog box to be displayed which enables the user to enter a String for the program to operate on.
A variable of type String is like a box in memory into which you can place Strings.
The value of the expression "12" + "14" is "26".
The declaration Integer x; creates a primitive type variable in which you can store integers.
The Java API is a useful collection of classes that you may use in your programs.
Assigning one String reference variable to another causes both to contain the address of the same String object.
Dry running a program means running it without any input data.
Dry running is best carried out using a table.