Java Numbers and Strings

Adding Numbers and Strings

Important Note: Java uses the + operator for both addition and concatenation.

• When you add numbers, the result is their sum.
• When you add strings, the result is their concatenation (joining).

Adding Numbers

If you add two numbers, you’ll get a numeric result:

Example

int a = 10;
int b = 20;
int result = a + b;  // result will be 30 (an integer/number)

int a = 10;

int b = 20;

int result = a + b;  // result will be 30 (an integer/number)

Adding Strings

If you add two strings, you’ll get a concatenated string:

Example

String num1 = "10";
String num2 = "20";
String concatenatedResult = num1 + num2;  // concatenatedResult will be "1020" (a String)

String num1 = "10";

String num2 = "20";

String concatenatedResult = num1 + num2;  // concatenatedResult will be "1020" (a String)

Adding a Number and a String

If you add a number and a string, the result will still be a concatenated string:

Example

String numStr = "10";
int num = 20;
String combinedResult = numStr + num;  // combinedResult will be "1020" (a String)

String numStr = "10";

int num = 20;

String combinedResult = numStr + num;  // combinedResult will be "1020" (a String)

Additional Information

String concatenation in Java can be performed using several methods. Besides using the + operator, you can use methods such as StringBuilder or StringBuffer for more efficient concatenation in loops or large applications.

Example with StringBuilder

StringBuilder stringBuilder = new StringBuilder();
stringBuilder.append("The result is: ");
stringBuilder.append(30);
System.out.println(stringBuilder.toString());  // Outputs "The result is: 30"

StringBuilder stringBuilder = new StringBuilder();

stringBuilder.append("The result is: ");

stringBuilder.append(30);

System.out.println(stringBuilder.toString());  // Outputs "The result is: 30"

Efficiency Note

Using StringBuilder or StringBuffer is recommended for better performance when concatenating strings in loops or when dealing with large strings.