3.4. (Static) Method Summary

This chapter has introduced static methods: those used in procedural programming as opposed to instance-methods used to implement object-oriented programming.

3.4.1. Method definition

  1. The general syntax for defining a static method is

    static returnTypeOrVoid MethodName ( parameter list )
    {
    statements in the method body…
    }

  2. The parameter list can be empty or contain one or more comma separated parameter entries. Each parameter entry has the form

    type parameterName

  3. If the method is going to be called from outside its class, the heading needs to start with public before the static.

  4. If returnTypeOrVoid in the heading is not void, there must be a return statement in the method body. A return statement has the form

    return expression ;

    where the expression should be of the same type as in returnTypeOrVoid. Execution of the method terminates immediately when a return statement is reached.

  5. Execution of a program starts at a method with a heading including

    static void Main

3.4.2. Method Calls

  1. A method call takes the form

    MethodName ( actual parameter list )

    A method call makes the method definition be executed.

  2. The actual parameter list is a comma separated list of the same length as the parameter list. Each entry is an expression. The entries in an actual parameter list do not include type declarations.

    Effectively, the method execution starts by assigning to each parameter variable the corresponding value from evaluating the actual parameter expression. In particular, that means the actual parameter values must be allowed in an assignment statement for a variable of the parameter’s type!

  3. If the method has return type void, it can only be used syntactically as an entire statement (with a semicolon added). After the method call completes, execution continues with the next statement.

  4. If there is a non-void return type, then the method call is syntactically an expression in the statement where is appears. The execution of such a method must reach a return statement. The value of the method-call expression is the value of the expression in this return statement.

  5. A method with a return value can also legally be used as a whole statement. In this case the return value is lost. Though legal, this is often an error!

3.4.3. Scope

  1. A variable declared inside a method definition is called a local variable. This declaration may be in either the parameter list or in the body of the method.

  2. A local variable comes into existence after the method is called, and ceases to exist after that method call terminates. A local variable is invisible to the rest of the program. Its scope is just within that method. Its lifetime is just through a single method call. Its value may be transferred outside of the method scope by standard means, principally:

    • If it is the expression in a return statement, its value is sent back to the caller.

    • It can be passed as an actual parameter to a further method called within its scope.

3.4.4. Static Variables

  1. There may be a declaration prefaced by the word static that appears inside a class and outside of any method definition in the class. Static variables are visible within each method of the class, and may be used by the methods.

  2. A common use of a static variable is to give a name to a constant value used in multiple methods in the class.