Joining strings using separator in Java

Question

I have an object called MyDate and it return three methods String getDay(), String getYear(), String getMonth()

For example Sep 24 2013 will 2013, 24, 9 .. I want to join these three strings using a common separator which is DASH "-". How do I join without using StringBuilder or "+" operator ? What would be the most compact code form ?

For e.g I know I can do this but is there a more compact form ? Because I know + operator is expensive.

MyDate myDate = new MyDate();
myDate.getYear()+"-"+myDate.getMonth()+"-"+myDate.getDay();

I'd say use a StringBuilder, but you exluded that. How come? — jedwards
– jedwards, Commented Sep 25, 2013 at 0:55

Hovercraft Full Of Eels · Accepted Answer · 2013-09-25 00:55:07Z

2

You could use String.format(...)

For example, if your getXXX() methods return a Strings:

String dateStr = String.format("%s-%s-%s", 
      myDate.getYear(), myDate.getMonth(), myDate.gateDay());

Else if they return an int:

String dateStr = String.format("%4d-%02d-%02d", 
      myDate.getYear(), myDate.getMonth(), myDate.gateDay());

For more on this, check out any tutorial on the printf(...) method or the Formatter object.

answered Sep 25, 2013 at 0:55

Hovercraft Full Of Eels

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Sotirios Delimanolis · Accepted Answer · 2013-09-25 00:59:15Z

2

You can be cool and use Guava

public static void main(String[] args) {
    Date myDate = new Date();
    Object[] objects = new Object[] {
            myDate.getYear(), myDate.getMonth(), myDate.getDay()
    };
    String message = Joiner.on("-").join(objects);
    System.out.println(message);
}

answered Sep 25, 2013 at 0:59

Sotirios Delimanolis

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4 Comments

user949300 Over a year ago

One suspects that Guava uses StringBuilder.

Sotirios Delimanolis Over a year ago

@user949300 Yeah, but it's hidden!

user949300 Over a year ago

I like your solution, or the Apache commons suggestions, assuming that OP is already using them in his codebase.

arun Over a year ago

Wish Joiner.on("-").join(objects); was named Joiner.join(objects).using("-");

Aurand · Accepted Answer · 2013-09-25 01:04:06Z

2

If you're not opposed to using Apache commons.

StringUtils#join

answered Sep 25, 2013 at 1:04

Aurand

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Crickcoder · Accepted Answer · 2013-09-25 01:07:12Z

0

If you can use apache commons then String concatenate(Object[] array) would be perfect. You can give your strings in one go :

StringUtils.concatenate([myDate.getYear(), myDate.getMonth(), myDate.gateDay()])

More info here : http://commons.apache.org/proper/commons-lang/javadocs/api-2.6/org/apache/commons/lang/StringUtils.html

answered Sep 25, 2013 at 1:07

Crickcoder

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1 Comment

Sotirios Delimanolis Over a year ago

Don't you need a separator somewhere in there? Also that method is deprecated.

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