Switch expressions: Why does Java consider my break - String lines not to be statements?

Question

Trying to understand switch expression and came up with the following code. In fact I get "not a statement" error for all "break - String" combinations. What am I doing wrong?

String i = switch(value) {
            case 0:
                break "Value is 0";
            case 1:
                break "Value is 1";
            case 2:
                break "Value is 2";
            default:
                break "Unknown value";
        };

https://docs.oracle.com/en/java/javase/13/language/switch-expressions.html: "To specify their value, use the new yield statement instead of the break statement." — Andy Turner, Apr 05 '21 at 12:38

score 7 · Accepted Answer · answered Apr 05 '21 at 12:45

7

The correct keyword to use is yield to return a value in a switch expression: it was introduced as an enhancement in JDK 13. Alternatively since your expressions are all simple you can use the shorthand arrow notation:

String i = switch(value) {
    case 0 -> "Value is 0";
    case 1 -> "Value is 1";
    case 2 -> "Value is 2";
    default -> "Unknown value";
};

answered Apr 05 '21 at 12:45

M A

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1

Thanks a lot. I am aware of arrow notation and was able to produce it without error. I was not aware about yield. Strange, I'm learning with oReilly Learning Java book and it claims to be fully updated for Java 14. That was misleading. Your answer however sorted my issue. Thank you. – vdmclcv Apr 05 '21 at 12:58
Nice! @vdmclcv - You can also check [What are switch expressions and how are they different from switch statements?](https://stackoverflow.com/q/65657169/10819573) – Arvind Kumar Avinash Apr 05 '21 at 13:04

Yegorf · Answer 2 · 2021-04-05T12:59:49.847

-2

For JDK < 13

    String i;
    switch(value) {
        case 0:
            i = "Value is 0";
            break;
        case 1:
            i = "Value is 1";
            break;
        case 2:
            i = "Value is 2";
            break;
        default:
            i = "Unknown";
    };

For JDK > 13:

String i = switch(value) {
    case 0 -> "Value is 0";
    case 1 -> "Value is 1";
    case 2 -> "Value is 2";
    default -> "Unknown";
};

Your example - is the combination of sitch statement and expression :)

edited Apr 05 '21 at 12:59

answered Apr 05 '21 at 12:41

Yegorf

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Can you modify your answer @yegorf, it is misleading – Yassin Hajaj Apr 05 '21 at 12:43
But what you're showing is a switch statement not a switch expression and yes, his example comes from Java – Yassin Hajaj Apr 05 '21 at 12:48
Not all java versions have a switch expression. – Yegorf Apr 05 '21 at 12:51
What you're saying is `Your example is not from Java language`, well, yes it is. Please modify your answer as this one is misleading – Yassin Hajaj Apr 05 '21 at 12:52

Switch expressions: Why does Java consider my break - String lines not to be statements?

2 Answers2