Java add string

last modified July 10, 2024

In this article we show how to concatenate strings in Java.

In Java, a string is a sequence of Unicode characters. Strings are objects. There are two basic classes for working with strings:

There are several ways how to add strings in Java:

• • operator

• concat method

• String.join method

• StringBuilder append method

• String.format

Using the + operator

The easiest way of concatenating strings is to use the + or the += operator. The + operator is used both for adding numbers and strings; in programming we say that the operator is overloaded.

Main.java

void main() {

System.out.println("Return" + " of " + "the king.");

String msg = "There are";
msg += " three";
msg += " falcons";
msg += " in the sky";

System.out.println(msg);

}

The example adds two strings using the + and += operators.

$ java Main.java Return of the king. There are three falcons in the sky

Java add strings with String.concat

The String.concat method concatenates the specified string to the end of this string.

Main.java

void main() {

System.out.println("Return".concat(" of ").concat("the king."));

}

In the example, we add strings with String.concat.

Using String.join

The String.join method returns a new atring composed of copies of the CharSequence elements joined together with a copy of the specified delimiter.

Main.java

void main() {

String[] words = { "There", "are", "two", "owls", "on", "the", "tree" };
String msg = String.join(" ", words);

System.out.println(msg);

}

We have an array of words. We form a sentence from the words with the String.join method.

$ java Main.java There are two owls on the tree

Using StringBuilder

StringBuilder is a mutable sequence of characters. Its append method appends the specified string to the string instance.

Main.java

void main() {

var sb = new StringBuilder();
sb.append("Return");
sb.append(" of ");
sb.append("the king.");

System.out.println(sb);

}

In the example, we form a new string with StringBuilder.

$ java Main.java Return of the king.

Using String.format

The String.format method returns a formatted string using the specified format string and arguments.

Main.java

void main() {

var w1 = "three";
var w2 = "owls";

var msg = String.format("There are %s %s on the tree", w1, w2);
System.out.println(msg);

}

In the example, we build a new string with String.format.

Source

Java String - language reference

In this article we have showed how to add strings in Java.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

List all Java tutorials.