Expression and Statements in Java(ICSE Computer Applications Notes)

Expressions, Statements and Displaying Data in Java 

Expression: Java is one of the most powerful and widely used programming languages. While writing programs in Java, we frequently use expressions to perform calculations and operations. An expression in Java is a combination of variables, constants, operators, and method calls that produces a single value when evaluated. In simple words, an expression is a statement that calculates a value.

Components of a Java Expression:

1. Variables: In Java, a variable is a container that is used to store data values. Each variable has a specific data type which determines what kind of value it can hold.

Example:

int a = 5;
int b = 10;
int c = a + b;

Here a + b is an expression.

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2. Constants: 

In Java, constants are variables whose values cannot be changed once they are assigned. They are declared using the final keyword.

In simple terms, a constant is a fixed value that remains the same throughout the program.

Example

int result = 5 * 6;

Here 5 * 6 is an expression.

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3. Operators

Operators in Java are special symbols used to perform operations on variables and values. They help in performing mathematical calculations, comparisons, and logical operations.

Types of Expressions in Java

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1. Arithmetic Expression

An arithmetic expression in Java is a combination of variables, constants, and arithmeticoperators that performs a mathematical calculation and produces a numeric result. In simple words, an arithmetic expression is used to perform mathematical operations in a Java program.

Operators Used

+ Addition
- Subtraction
* Multiplication
/ Division

% Modulus (remainder)

Example

int a = 10;
int b = 5;
int result = a * b + 20;

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2. Relational Expression

A relational expression in Java is an expression that compares two values using relational operators and returns a boolean result (true or false).

In simple words, a relational expression checks the relationship between two operands.

Example

int a = 15;
int b = 10;

boolean result = a > b;

Output: true

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3. Logical Expression

A logical expression in Java is an expression that combines two or more relational expressions using logical operators and produces a boolean result (true or false).

In simple terms, logical expressions are used to check multiple conditions at the same time.

Logical Operators

&& Logical AND
|| Logical OR
! Logical NOT

Example

int age = 20;
boolean result = age > 18) && (age < 60);

Output: true

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4. Assignment Expression

An Assignment Expression in Java is an expression where a value or result of another expression is assigned to a variable using the assignment operator (=).

It stores the result of the expression on the right side into the variable on the left side.

Example:

int x;
x = 50;

Here

x = 50

is an assignment expression.

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5. Increment and Decrement Expression

An Increment Expression increases the value of a variable by 1 using the increment operator (++).

A Decrement Expression decreases the value of a variable by 1 using the decrement operator (--).

Operators

++ Increment
-- Decrement

Example

int a = 10;
a++;

Value of a becomes 11.

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Example Program Using Expression

public class ExpressionExample
{
 public static void main(String args[])
 {
 int a = 10;
 int b = 5;

 int sum = a + b;
 int product = a * b;

 boolean check = a > b;

 System.out.println("Sum = " + sum);
 System.out.println("Product = " + product);
 System.out.println("Is a greater than b? " + check);
 }
}

Output:

Sum = 15
Product = 50
Is a greater than b? true

 

Statements in Java:

A Java statement is a complete command that performs an action during program execution. Most Java statements end with a semicolon ( ; ).

In Java programming, a statement is a single instruction that tells the computer to perform a specific task. Statements are the basic building blocks of a Java program. Every Java program is made up of one or more statements that are executed by the Java Virtual Machine (JVM).

Example

int a = 10;

Explanation:

·         int → data type

·         a → variable

·         = 10 → value assigned

·         ; → terminates the statement

Types of Statements

In Java, statements are generally classified into the following types:

1.     Assignment Statement

2.     Expression Statement

3.     Selection (Decision Making) Statement

4.     Iteration (Looping) Statement

5.     Jump Statement

Important Points About Java Statements

·  A Java statement usually ends with a semicolon ( ; ).

· Statements are executed one by one in a program.

· Statements help in controlling the flow of a program.

· Different types of statements are used for calculation, decision making, and looping.

Displaying Data in Java:

In Java programming, displaying data means showing information or output on the screen (console). This is an important concept for ICSE Computer Applications students because every Java program needs to display results, messages, or calculated values.

Methods Used to Display Data in Java

Java mainly uses the following methods to display data:

1.     print()

2.     println()

1. print() Method

The print() method displays the output but does not move the cursor to the next line.

Example:

System.out.print("Java ");
System.out.print("Programming");

Output

Java Programming

Both words appear on the same line.

2. println() Method

The println() method displays the output and moves the cursor to the next line.

Example

System.out.println("Java");
System.out.println("Programming");

Output

Java
Programming

Each statement appears on a new line.

Important Points:

· System is a predefined class in Java.

· out is an object used to display output.

· println() prints data and moves to the next line.

· print() prints data on the same line.

· + operator is used to combine text and variables.

 

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