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In computer programming languages, a switch statement is a type of selection control mechanism used to allow the value of a variable or expression to change the control flow of program execution via search and map. Switch statements function somewhat similarly to the if statement used in programming languages like C/C++, C#, Visual Basic .NET ...
switch (variable) { case case 1: instructions «break_or_jump_statement» ... «default: instructions break_or_jump_statement»} All non-empty cases must end with a break or goto case statement (that is, they are not allowed to fall-through to the next case). The default case is not required to come last.
The default keyword can optionally be used in a switch statement to label a block of statements to be executed if no case matches the specified value; see switch. [9] [10] Alternatively, the default keyword can also be used to declare default values in a Java annotation.
Switch statements can allow compiler optimizations, such as lookup tables. In dynamic languages, the cases may not be limited to constant expressions, and might extend to pattern matching, as in the shell script example on the right, where the *) implements the default case as a glob matching any string.
Java SE 8 introduced default methods to interfaces which allows developers to add new methods to existing interfaces without breaking compatibility with the classes already implementing the interface. Unlike regular interface methods, default methods have a body which will get called in the case if the implementing class doesn't override it.
Switch statements can allow compiler optimizations, such as lookup tables. In dynamic languages, the cases may not be limited to constant expressions, and might extend to pattern matching, as in the shell script example on the right, where the '*)' implements the default case as a regular expression matching any string.
This illustrates an alternative method of specifying the default case, which can appear first, last, or anywhere in between. If no default is specified and no case matches the supplied value, a null value is returned. For each branch of a #switch, either side of an equals-sign "=" can be a simple value, an expression, or a template call.
For function that manipulate strings, modern object-oriented languages, like C# and Java have immutable strings and return a copy (in newly allocated dynamic memory), while others, like C manipulate the original string unless the programmer copies data to a new string.