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Java String concat()
In this tutorial, we will learn about the Java String concat() method with the help of examples.
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". |
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