Java Arithmetic Operators

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Index:

1. Arithmetic Operators
2. Arithmetic Operators on Numbers
3. Arithmetic Operators on Chars
4. Arithmetic Operators on Strings

• [[#concatenation-with—operator|Concatenation with + Operator]]
• Concatenation of Strings with Other Data Types
• Implicit Conversion in Concatenation
• Special Case Concatenation Order Matters

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Arithmetic Operators

Arithmetic operators are used to perform arithmetic operations on variables and data. For example,

a + b;

Here, the + operator is used to add two variables a and b. Similarly, there are various other arithmetic operators in Java.

Operator	Operation
+	Addition
-	Subtraction
*	Multiplication
/	Division
%	Modulo Operation (Remainder after division)

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Arithmetic Operators on Numbers

 
int a = 12, b = 5;
 
a + b    // 17
 
a - b    // 7
 
a * b    // 60
 
a / b    // 2 
 
a % b    // 2

Division Operator

• Division two integers ⇒ Result: integer
• Division floating-point with at least one floating-point ⇒ Result: floating-point

(9 / 2) is 4
(9.0 / 2) is 4.5
(9 / 2.0) is 4.5
(9.0 / 2.0) is 4.5

int a = 9;
int b = 2;
 
System.out.println(a/b);             // output: 4
System.out.println((float)(a/b));    // output: 4.0
System.out.println((float)(a)/b);    // output: 4.5

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Arithmetic Operators on Chars

When you perform an arithmetic operation on a char, it gets implicitly cast to an int value. This int value corresponds to the Unicode value of the character.

Here’s an example:

public class Main {
 
    public static void main(String[] args) {
 
		char a = 'z';   // Unicode value: 122
        char b = '!';   // Unicode value: 33
    
        int  r1 = a-b;  // 89
        char r2 = a+b;  // ERROR: incompatible types
        char r3 = (char)(a-b);    // 'Y'
        
        int  r4 = a+1;   // 123
        char r5 = a+1;   // ERROR: incompatible types
        char r6 = (char)(a+1);   // '{'
    }
}

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Arithmetic Operators on Strings

In Java, strings are objects that represent sequences of characters. The Java platform provides the String class to create and manipulate strings. While arithmetic operators like +, -, *, /, and % are not directly applicable in the same way as they are with numeric data types, the + operator can be used with strings, but it behaves differently. It is used for concatenation, which means joining strings together end-to-end to create a new string.

Concatenation with + Operator

String a = "Hello, ";
String b = "world!";
 
String c = a + b;  // "Hello, world!"

The + operator can also be used to concatenate strings with other data types. When one of the operands is a string, the + operator concatenates the string representation of the other operand.

String str = "Year: ";
int year = 2023;
 
String result = str + year;  // "Year: 2023"

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Implicit Conversion in Concatenation

When using the + operator with mixed data types where at least one operand is a string, Java automatically converts the other operand to its string representation before concatenation.

String message = "Score: " + 100;  // "Score: 100"

In this case, the integer 100 is automatically converted to the string "100" before it is concatenated with the string "Score: ".

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Special Case: Concatenation Order Matters

When concatenating strings with other types in a single expression, the result might depend on the order and grouping of the operations due to how expressions are evaluated from left to right.

System.out.println("Sum: " + 10 + 20);  // "Sum: 1020"
System.out.println("Sum: " + (10 + 20));  // "Sum: 30"

In the first line, the string "Sum: " is concatenated with 10 resulting in "Sum: 10", which is then concatenated with 20, resulting in the string "Sum: 1020". In the second example, because of the parentheses, 10 + 20 is evaluated first, resulting in 30, which is then concatenated with "Sum: ", producing the expected result of "Sum: 30".

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Concatenation of Characters and Strings

In Java, the char data type represents a single character. Unlike strings, when you try to concatenate two char values using the + operator, the result is not a string concatenation but a numeric addition, because char values are treated as integers.

char a = 'A'; // Unicode value: 65
char b = 'B'; // Unicode value: 66
 
int result2 = a + b;  // 131, not "AB"
String result1 = a + b; // error: incompatible types
 

To concatenate char values as strings, you can prepend or append an empty string ("") to the expression. This forces Java to treat the operation as string concatenation rather than numeric addition.

char a = 'A';
char b = 'B';
 
String result = "" + a + b;  // "AB"

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