Java 12 has enhanced Switch expressions for Pattern matching.
Introduced in JEP 325, as a preview language feature, the new Syntax is L ->.
Following are some things to note about Switch Expressions:
• The new Syntax removes the need for break statement to prevent fallthroughs.
• Switch Expressions don’t fall through anymore.
• Furthermore, we can define multiple constants in the same label.
• default case is now compulsory in Switch Expressions.
• break is used in Switch Expressions to return values from a case itself.
Classic switch statement:
String result = "";
switch (day) {
case "M":
case "W":
case "F": {
result = "MWF";
break;
}
case "T":
case "TH":
case "S": {
result = "TTS";
break;
}
};
System.out.println("Old Switch Result:");
System.out.println(result);
With the new Switch expression, we don’t need to set break everywhere thus prevent logic errors!
String result = switch (day) {
case "M", "W", "F" -> "MWF";
case "T", "TH", "S" -> "TTS";
default -> {
if(day.isEmpty())
break "Please insert a valid day.";
else
break "Looks like a Sunday.";
}
};
System.out.println(result);
Let’s run the below program containing the new Switch Expression using JDK 12.
public class SwitchExpressions {
public static void main(String[] args)
{
System.out.println("New Switch Expression result:");
executeNewSwitchExpression("M");
executeNewSwitchExpression("TH");
executeNewSwitchExpression("");
executeNewSwitchExpression("SUN");
}
public static void executeNewSwitchExpression(String day){
String result = switch (day) {
case "M", "W", "F" -> "MWF";
case "T", "TH", "S" -> "TTS";
default -> {
if(day.isEmpty())
break "Please insert a valid day.";
else
break "Looks like a Sunday.";
}
};
System.out.println(result);
}
}
Since this is a preview feature, please ensure that you have selected the Language Level as Java 12 preview.
To compile the above code run the following command:
javac -Xlint:preview --enable-preview -source 12 src/main/java/SwitchExpressions.java
After running the compiled program, we get the following in the console
Java Switch Expressions Program Output
Switch expressions is a preview language feature. This means that even though it is complete, it may not be confirmed in the future Java Release.
