Preface
For Java beginners, the switch-case structure is a very useful control flow statement that allows us to execute different code blocks based on the value of an expression. Below, we will introduce in detail the usage methods and precautions of switch-case structure.
1. Basic syntax of switch-case structure
The basic syntax of the switch-case structure is as follows:
switch (expression) {
case value1:
// If the value of the expression is equal to the value 1, execute the code here break; // Optional, used to terminate switch structure case value2:
// If the value of the expression is equal to the value 2, execute the code here break; // Optional, used to terminate switch structure // ... There can be more case branches default:
// If the value of the expression does not match any case branch, execute the code here}
In the switch statement, the value of the expression is compared to the value of each case tag. When a matching case is found, the code behind the case will be executed until the end of the break statement or switch structure is encountered. If no case matches, the default branch code is executed (if it exists).
2. Use examples
Here is a simple example showing how to use the switch-case structure:
public class SwitchCaseExample {
public static void main(String[] args) {
int day = 3; // Assume this is obtained from a method or user input
switch (day) {
case 1:
("Monday");
break;
case 2:
("Tuesday");
break;
case 3:
("Wednesday");
break;
case 4:
("Thursday");
break;
case 5:
("Friday");
break;
case 6:
("Saturday");
break;
case 7:
("Sunday");
break;
default:
("Invalid date value");
}
}
}
In this example, we output the corresponding day of the week based on the value of the variable day. If the value of day is an integer between 1 and 7, the corresponding day of the week will be output; if the value of day is not within this range, the "invalid date value" will be output.
3. Things to note
Type Match: The type of the switch expression must be byte, short, char, int, enum type (enum), String or the wrapper type (Byte, Short, Character, Integer) supported since Java 7.
fall-through: In Java, if the break statement is not used behind the case branch, the program will continue to execute the code of the next case branch, which is called the fall-through phenomenon. To avoid unnecessary errors, it is usually recommended to use break statements at the end of each case branch.
default branch: The default branch is optional, but if your switch structure may not handle all possible values, it is recommended to include the default branch to handle unexpected situations.
switch expression: Starting in Java 12, you can also use switch expressions (also known as "switch in the form of trigonometric operators"), which allows you to return or assign values to variables more concisely.
4. Summary
The switch-case structure is a very efficient way to handle multiple branch conditions in Java. By using the switch-case structure rationally, we can write clearer and easier to maintain code. I hope that the introduction and examples of this article can help beginners better understand and apply switch-case structure.
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