How do I concatenate two strings in Java?

Question

I am trying to concatenate strings in Java. Why isn\'t this working?

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Answer 1

There are two basic answers to this question:

1. [simple] Use the + operator (string concatenation). "your number is" + theNumber + "!" (as noted elsewhere)
2. [less simple]: Use StringBuilder (or StringBuffer).

StringBuilder value;
value.append("your number is");
value.append(theNumber);
value.append("!");

value.toString();

I recommend against stacking operations like this:

new StringBuilder().append("I").append("like to write").append("confusing code");

Edit: starting in java 5 the string concatenation operator is translated into StringBuilder calls by the compiler. Because of this, both methods above are equal.

Note: Spaceisavaluablecommodity,asthissentancedemonstrates.

Caveat: Example 1 below generates multiple StringBuilder instances and is less efficient than example 2 below

Example 1

String Blam = one + two;
Blam += three + four;
Blam += five + six;

Example 2

String Blam = one + two + three + four + five + six;