How do I concatenate two strings in Java?

Question

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

public class StackOverflowTest {  
    public static void main(String args[]) {
                


        

Answer 1

The java 8 way:

StringJoiner sj1 = new StringJoiner(", ");
String joined = sj1.add("one").add("two").toString();
// one, two
System.out.println(joined);


StringJoiner sj2 = new StringJoiner(", ","{", "}");
String joined2 = sj2.add("Jake").add("John").add("Carl").toString();
// {Jake, John, Carl}
System.out.println(joined2);

Answer 2

here is an example to read and concatenate 2 string without using 3rd variable:

public class Demo {
    public static void main(String args[]) throws Exception  {
        InputStreamReader r=new InputStreamReader(System.in);     
        BufferedReader br = new BufferedReader(r);
        System.out.println("enter your first string");
        String str1 = br.readLine();
        System.out.println("enter your second string");
        String str2 = br.readLine();
        System.out.println("concatenated string is:" + str1 + str2);
    }
}

Answer 3

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;

Answer 4

You must be a PHP programmer.

Use a + sign.

System.out.println("Your number is " + theNumber + "!");

Answer 5

You can concatenate Strings using the + operator:

String a="hello ";
String b="world.";
System.out.println(a+b);

Output:

hello world.

That's it

Answer 6

For better performance use str1.concat(str2) where str1 and str2 are string variables.