A switch case in Java is a multi-way branch statement that allows a variable to be tested against a list of values. It is a control statement that evaluates an expression and executes code based on the value of the expression. The expression can be of a primitive data type such as int, char, short, byte, and char, and with JDK7, it can also work with the string and wrapper class and enumerated data type (enum in java) . The switch statement works like an if-else ladder, where multiple conditions can be checked at once. The switch statement evaluates its expression, then executes all statements that follow the matching case label. The body of a switch statement is known as a switch block, and a statement in the switch block can be labeled with one or more case or default labels.

Some important rules for switch statements include:

• There can be any number of cases, but duplicate case values are not allowed.
• The value for a case must be of the same data type as the variable in the switch.
• The value for a case must be constant or literal. Variables are not allowed.

The break statement is used to terminate the statement sequence inside the switch, and the default keyword handles all values that are not explicitly handled by one of the case sections.

Java 12 added the switch expression as an experimental feature, which is a switch statement that can return a value.

In summary, a switch case in Java is a control statement that evaluates an expression and executes code based on the value of the expression. It works like an if-else ladder and can handle multiple conditions at once. The switch statement works with byte, short, int, long, enum, string, and wrapper classes.