Java constructor chaining and avoid code repetition

Question

I have immutable class and want add new constructor without duplicating code in both constructors.

I have class:

public class Test { private final String stringParameter; public Test() { stringParameter = "firstReallyLongDefaultString"; } public Test(String s) { stringParameter = s; } }

And I want to add the new constructor with "char" parameter, something like this:

public Test(char s) { if(Character.isLetter(s)) { stringParameter = "firstReallyLong" + s + "DefaultString"; } else { stringParameter = "firstReallyLongDefaultString"; } }

How can I do it without the code repetition of the long string? I would like to call "this()" constructor in else branch but it's not possible.

Dev Blanked · Accepted Answer · 2013-04-18 11:37:44Z

2

public Test(char s) { this(Character.isLetter(s) ? "firstReallyLong" + s + "DefaultString" : "firstReallyLongDefaultString"); }

answered Apr 18, 2013 at 11:37

Dev Blanked

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3 Comments

Vincent van der Weele Over a year ago

this doesn't answer the question... the string firstReallyLongDefaultString still needs to be repeated in this constructor

Dev Blanked Over a year ago

@Heuster that can easily be moved to a static constant

Vincent van der Weele Over a year ago

That would answer the question (unless the original constructor cannot be altered)

kan · Accepted Answer · 2013-04-18 12:28:27Z

You also could chain them more explicitly, removing some code repetition:

public class Test { private static final String DEFAULT_VALUE = "firstReallyLongDefaultString"; private final String stringParameter; public Test() { this(DEFAULT_VALUE); } public Test(String s) { stringParameter = s; } public Test(char c) { this(prepareString(c)); } private static String prepareString(char c) { if(Character.isLetter(s)) { return "firstReallyLong" + s + "DefaultString"; } else { return DEFAULT_VALUE; } } }

The "firstReallyLongDefaultString" better to be done as a private constant to avoid repetition.

user207421 · Accepted Answer · 2013-04-18 11:35:37Z

1

Like this:

public Test(char s) { super(); if(Character.isLetter(s)) { stringParameter = "firstReallyLong" + s + "DefaultString"; } }

answered Apr 18, 2013 at 11:35

user207421

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2 Comments

Dev Blanked Over a year ago

This doesn't seem to compile

Robert Balent Over a year ago

The property is final, this will not compile.

WilQu · Accepted Answer · 2013-04-18 12:12:45Z

A factory method gives you more flexibility:

public static Test create(char c) { final String parameter; if(Character.isLetter(s)) { parameter = "firstReallyLong" + s + "DefaultString"; } else { parameter = "firstReallyLongDefaultString"; } return new Test(parameter); }

This can't be inherited in subclasses, however if you want your class to be strictly immutable it should be final.

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