javaswitchcase变量

Introduction

Java switch case statement is used to execute a block of code based on certain conditions. The switch statement evaluates the value of a variable and performs actions based on different cases. It is a powerful tool that can simplify the code and make it easier to read and maintain. In this article, we will explore the use of variables with the switch case statement in Java.

Using variables in switch case

The switch case statement in Java can use variables of various data types, including char, byte, short, int, and enum. The variable must have a single value that can be compared with the values in the cases. The following is an example of using a variable in a switch case statement:

int day = 2;
switch (day) {
    case 1:
        System.out.println("Monday");
        break;
    case 2:
        System.out.println("Tuesday");
        break;
    case 3:
        System.out.println("Wednesday");
        break;
    default:
        System.out.println("Other day");
}

In this example, the variable "day" is of type int and has the value 2. The switch case statement evaluates the value of the variable and executes the corresponding case. In this case, it prints "Tuesday."

Note on using variables in switch case

There are a few things to keep in mind when using variables with the switch case statement in Java. First, the variable must be initialized before it is used in the switch statement. Second, the variable must be a primitive data type, an enumerated type, or a String. Third, the variable can only be compared with constant values in the cases. Finally, each case must end with a break statement to avoid fall-through, which means executing the code in the next cases.

The following is an example of using a variable of type String in a switch case statement:

String fruit = "banana";
switch (fruit) {
    case "apple":
        System.out.println("It is an apple");
        break;
    case "banana":
        System.out.println("It is a banana");
        break;
    case "orange":
        System.out.println("It is an orange");
        break;
    default:
        System.out.println("It is not a fruit");
}

In this case, the variable "fruit" is of type String and has the value "banana." The switch case statement evaluates the value of the variable and executes the corresponding case. In this case, it prints "It is a banana."

Conclusion

The switch case statement in Java is a powerful tool that can simplify the code and make it easier to read and maintain. It can use variables of various data types, including char, byte, short, int, enum, and String. The variable must be initialized, and each case must end with a break statement. By understanding these rules, developers can take full advantage of the switch case statement in their Java programs.