String Concatenation

You can use + operator to concatenate strings together.

For example, the following fragment concatenates three strings:

 
public class Main {
  public static void main(String[] argv) {
    String age = "9";
    String s = "He is " + age + " years old.";
    System.out.println(s);
  }
}

He is 9 years old.

Use string concatenation to create a very long string.

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

    String longStr = "A java 2s.      com" + 
                     "B j a v a 2 s . c o m                     " + 
                     "C java                 2s.com" + 
                     "D java2s.com .";

    System.out.println(longStr);
  }
}

A java 2s.      comB j a v a 2 s . c o m                     C java                 2s.comD java2s.com .

String Concatenation with Other Data Types

You can concatenate strings with other types of data.

 
public class Main {
  public static void main(String[] argv) {
    int age = 1;
    String s = "He is " + age + " years old.";
    System.out.println(s);
  }
}

The output:


He is 1 years old.

Be careful when you mix other types of operations with string concatenation. Consider the following:

 
public class Main {
  public static void main(String[] argv) {
    String s = "four: " + 2 + 2;
    System.out.println(s);
  }
}

This fragment displays


four: 22

rather than the


four: 4

To complete the integer addition first, you must use parentheses, like this:


String s = "four: " + (2 + 2);

Now s contains the string "four: 4".

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