The concat() method concatenates (joins) two strings and returns it.
Example
class Main {
public static void main(String[] args) {
String str1 = "Java";
String str2 = "Programming";
// concatenate str1 and str2
System.out.println(str1.concat(str2));
}
}
// Output: JavaProgramming
Syntax of concat()
The syntax of the string concat() method is:
string.concat(String str)
Here, string is an object of the String class.
concat() Parameters
The concat() method takes a single parameter.
- str - string to be joined
concat() Return Value
- returns a string which is the concatenation of
stringandstr(argument string)
Example: Java concat()
class Main {
public static void main(String[] args) {
String str1 = "Learn ";
String str2 = "Java";
// concatenate str1 and str2
System.out.println(str1.concat(str2)); // "Learn Java"
// concatenate str2 and str11
System.out.println(str2.concat(str1)); // "JavaLearn "
}
}
Using + Operator for Concatenation
In Java, you can also use the + operator to concatenate two strings. For example,
class Main {
public static void main(String[] args) {
String str1 = "Learn ";
String str2 = "Java";
// concatenate str1 and str2
System.out.println(str1 + str2); // "Learn Java"
// concatenate str2 and str11
System.out.println(str2 + str1); // "JavaLearn "
}
}
concat() Vs the + Operator for Concatenation
| concat() | the + Operator |
|---|---|
Suppose, str1 is null and str2 is "Java". Then, str1.concat(str2) throws NullPointerException. |
Suppose, str1 is null and str2 is "Java". Then, str1 + str2 gives "nullJava". |
You can only pass a String to the concat() method. |
If one of the operands is a string and another is a non-string value. The non-string value is internally converted to a string before concatenation. For example, "Java" + 5 gives "Java5". |