Why Java 14’s New Switch Expression and Null‑Pointer Messages Matter

Java 13 was released in September 2019 with almost no useful features, so we skip it and go straight to Java 14 .

Switch expression

The traditional switch statement is verbose and often hides bugs because of the required break statements. An example of the old style is shown below.

switch (day) {
    case MONDAY:
    case FRIDAY:
    case SUNDAY:
        System.out.println(6);
        break;
    case TUESDAY:
        System.out.println(7);
        break;
    case THURSDAY:
    case SATURDAY:
        System.out.println(8);
        break;
    case WEDNESDAY:
        System.out.println(9);
        break;
    default:
        System.out.println(11);
}

Because of its noise, the author prefers to avoid the classic switch expression.

New switch label

Java 14 introduces the case L -> label, allowing multiple constants separated by commas and eliminating the need for break. The same logic can be written as:

switch (day) {
    case MONDAY, FRIDAY, SUNDAY -> System.out.println(6);
    case TUESDAY               -> System.out.println(7);
    case THURSDAY, SATURDAY    -> System.out.println(8);
    case WEDNESDAY             -> System.out.println(9);
    default                    -> System.out.println(11);
}

The right‑hand side of a case L -> label may be an expression, a block, or a throw statement. To return a value from a switch, you can write:

int numLetters = switch (day) {
    case MONDAY, FRIDAY, SUNDAY -> 6;
    case TUESDAY               -> 7;
    case THURSDAY, SATURDAY    -> 8;
    case WEDNESDAY             -> 9;
    default                    -> 11;
};

When a switch expression is assigned to a variable, the default branch is mandatory.

Yield restricted identifier

Inside a case that produces a value, the correct way to return the value is with the new yield keyword, not return. Example:

int numLetters = switch (day) {
    case WEDNESDAY -> {
        System.out.println("day = " + day);
        // yield is correct here
        yield 9;
    };
    default -> 11;
};

Improved Null‑Pointer messages

Before Java 14, a NullPointerException only reported the line number. Java 14 adds a more descriptive message that shows which variable was null, e.g.:

Exception in thread "main" java.lang.NullPointerException: Cannot store to int array because "arr" is null
    at cn.felord.SomeClass.main(SomeClass.java:17)

This makes it easier to pinpoint the source of the null pointer.

Other changes

Some preview features were not promoted and may be removed; readers can consult the official Java 14 release notes for details.

References

Java 14 release notes