Variables and data types

Primitive types, String, and casting.

Java is statically typed: every variable has a type that is fixed when you declare it, and the compiler checks it before the program runs.

Type	Holds
`int`	Whole numbers, about ±2.1 billion
`long`	Larger whole numbers. Write 5L
`double`	Decimal numbers
`boolean`	true or false
`char`	One character, in single quotes
`String`	Text, in double quotes. A class, not a primitive

Java

public class Main {
  public static void main(String[] args) {
    int age = 20;
    double cgpa = 8.4;
    boolean placed = false;
    char grade = 'A';
    String name = "Kavin";
    System.out.println(name + " " + age + " " + cgpa + " " + grade + " " + placed);
  }
}

Output

Kavin 20 8.4 A false

Casting and integer division

Dividing two ints drops the decimals, which is a classic exam trap. Cast one side to double to keep them.

Java

public class Main {
  public static void main(String[] args) {
    int a = 7, b = 2;
    System.out.println(a / b);
    System.out.println((double) a / b);
    System.out.println(a % b);
  }
}

Output

3
3.5
1

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