Cleaner handling of enums using new Switch expressions in Java 13

Use the new Switch expression in Java 13 for more concise processing of enumerations

In Java programming, we often use enumerations to represent a set of related constants. In the past, when dealing with enumerations, we usually used the traditional Switch statement. However, Java 13 brings us new Switch expressions, making the processing of enumerations more concise and flexible.

In this article, we will learn how to use the new Switch expression in Java 13 to work with enumerations and demonstrate its usage with code examples.

First, we need to define an enumeration that represents color, as shown below:

enum Color {
   RED, GREEN, BLUE;
}

Next, assume that we need to perform different operations based on different colors. In previous versions, we would usually use the traditional Switch statement to handle this situation as shown below:

Color color = Color.RED;
switch(color) {
   case RED:
      System.out.println("红色"); 
      break;
   case GREEN:
      System.out.println("绿色");
      break;
   case BLUE:
      System.out.println("蓝色");
      break;
   default:
      System.out.println("未知颜色");
}

However, in Java 13, we can use the new Switch expression to achieve the same Logic, the code is more concise, as shown below:

Color color = Color.RED;
String colorName = switch(color) {
   case RED -> "红色";
   case GREEN -> "绿色";
   case BLUE -> "蓝色";
   default -> "未知颜色";
};
System.out.println(colorName);

As can be seen from the code example, the new Switch expression uses the arrow operator -> to implement logical branches. Each branch can return a value and assign it to the colorName variable.

Also note that the new Switch expression can use the yield keyword to return a value, or the break keyword to terminate the branch. For example, we can rewrite the above code as follows:

Color color = Color.RED;
String colorName = switch(color) {
   case RED -> {
      yield "红色";
   }
   case GREEN -> {
      yield "绿色";
   }
   case BLUE -> {
      yield "蓝色";
   }
   default -> {
      yield "未知颜色";
   }
};
System.out.println(colorName);

In addition to the above examples, the new Switch expression also supports more usages, such as assigning the result to a variable and using expressions and methods Call etc.

In the process of using the new Switch expression, we also need to pay attention to some restrictions. For example, the result type of each branch must be consistent, cannot contain penetration behavior, each branch must cover all possible enumeration instances, etc.

In general, the new Switch expression in Java 13 brings us a more concise and flexible way to deal with enumerations. It provides a new syntax using arrow operators, making code easier to read and write.

I hope that through the above code examples, everyone can understand how to use the new Switch expression in Java 13 to process enumerations more concisely. At the same time, I also hope that this article can be helpful to everyone in daily Java development.

Reference:

• JEP 354: Switch Expressions (Preview)
• Java 13 Language Specification

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