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javaswitch-statementmultiple-return-values
Ori Marko
Ori Marko

Reputation: 58774

Java switch use case

I'm reluctant to use a switch, but I saw switch will be improved in Java 12

Java 12 added the switch expression as an experimental feature. A Java switch expression is a switch statement which can return a value.

The only use case I found (before Java 12) where switch may be useful is returning different values from a small closed set of cases, e.g.:

    switch (input) {
    case "A":
        return "1";
    case "B":
        return "2";
    default:
        return "0";
    }

Or in Java 12 example:

return
switch(digitInDecimal){
    case  0 -> '0';
    case  1 -> '1';
    case  2 -> '2';
    default -> '?';

But I found an old but high-ranked answer that says to avoid multiple return statements:

Assigning a value to a local variable and then returning that at the end is considered a good practice. Methods having multiple exits are harder to debug and can be difficult to read.

So I wonder, is that answer still relevant due to switch changes?

Must I wait for Java 12 where switch can be used without temporary variables and breaks?

Upvotes: 4

Views: 13649

Answers (2)

Rutger van Velzen
Rutger van Velzen

Reputation: 59

But I found an old but high-ranked answer that says to avoid multiple return statements:

Assigning a value to a local variable and then returning that at the end is considered a good practice. Methods having multiple exits are harder to debug and can be difficult to read.

So I wonder, is that answer still relevant due to switch changes?

This is a common misconception, it originates form the phrase: "Single entry, single exit." (Page 24) All this originates from an other era, one that lead to structured programming languages and eventually to object oriented programming languages (like Java).

Don't worry about multiple return statements, there is nothing wrong with it.

Upvotes: 2

Andrew
Andrew

Reputation: 49606

Assigning a value to a local variable and then returning that at the end is considered a good practice.

I have no idea when it was considered a good practice. To me, switch is usually * an indicator that a design error was made. I would rather put my effort into thinking how to avoid a switch than into wondering how to return a value from a switch.

A few examples

Long list of if statements in Java
How to avoid switch-case statements in Java
Converting many 'if else' statements to a cleaner approach

Methods having multiple exits are harder to debug and can be difficult to read.

The same goes for a method that has a lot of breaks - that's what you are going to do if you choose the "local-variable approach".

In my opinion, none of these

// 1
switch (input) {
    case "A":
        return "1";
    case "B":
        return "2";
    default:
        return "0";
}

// 2
String varibleToReturn = null;
switch (input) {
    case "A":
        varibleToReturn = "1";
        break;
    case "B":
        varibleToReturn = "2";
        break;
    default:
        varibleToReturn = "0";
}
return varibleToReturn;

// 3
return switch(digitInDecimal) {
    case  0 -> '0';
    case  1 -> '1';
    case  2 -> '2';
    default -> '?';
}

makes a significant difference, or a slight improvement. Yes, Java-12's switch would give more conciseness and expressiveness, but the fundamental idea remains the same.

Must I wait for Java 12 where switch can be used without temporary variables and breaks?

What does it mean? :) No, the deadline is tomorrow, you have to work with what you've got at hand now.

*I am not underestimating the usefulness of switch. It may come in handy, for instance, when you programme at low-level, or you write an optimization.

I am just saying that in the real world, with Springs, and Hibernates, in a world of patterns, switch is obsolescent.

Upvotes: 3

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