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Java 13 New features (JEP-355 Text Blocks (PREVIEW) (versions (Before …

Java 13 New features

JEP-355 Text Blocks
(PREVIEW)

versions

Before

 String html ="<html>\n" +
              "   <body>\n" +
              "      <p>Hello, World</p>\n" +
              "   </body>\n" +
              "</html>\n";


 String json ="{\n" +
              "   \"name\":\"mkyong\",\n" +
              "   \"age\":38\n" +
              "}\n";

After

 String html = """
                <html>
                    <body>
                        <p>Hello, World</p>
                    </body>
                </html>
                """;

 String json = """
                {
                    "name":"mkyong",
                    "age":38
                }
                """;

JEP-354

Switch Expressions (PREVIEW - This switch expression becomes a standard feature in Java 14 )

Before java 12

    private static String getText(int number) {
        String result = "";
        switch (number) {
            case 1, 2:
                result = "one or two";
                break;
            case 3:
                result = "three";
                break;;
            default:
                result = "unknown";
                break;
        };
        return result;
    }

in java 12 we can use break to return a value from a switch

    private static String getText(int number) {
        String result = switch (number) {
            case 1, 2:
                break "one or two";
            case 3:
                break "three";
            default:
                break "unknown";
        };
        return result;
    }

In Java 13, the above Java 12 value break is no longer compiled, we should use yield to return a value

    private static String getText(int number) {
        return switch (number) {
            case 1, 2:
                yield "one or two";
            case 3:
                // can do something here...
                System.out.println("Supports multi line block!");
                yield "four or five or six";
            default:
                yield "unknown";
        };
    }

Syntax with arrows from java 12 is still supported with yield.

    private static int getText(String mode) {
        int result = switch (mode) {
            case "a", "b" -> 1;
            case "d", "e", "f" -> {
                // do something here...
                System.out.println("Supports multi line block!");
                yield 3;
            }
            default -> -1;
        };
        return result;
    }

T result = switch (arg) {
    case L1 -> e1;
    case L2 -> e2;
    default -> e3;
};

We will extend the switch statement so it can be used as an expression. For example

static void howMany(int k) {
    System.out.println(
        switch (k) {
            case  1 -> "one"
            case  2 -> "two"
            default -> "many"
        }
    );
}