Strings & Math

String stores text. Use + to join strings (concatenation). length() returns character count.

Strings — working with text

String stores text. Use + to join strings (concatenation). length() returns character count.

Common methods: toUpperCase(), toLowerCase(), charAt(index), indexOf("text"), substring(start, end).

Real-life example: A String is a necklace of letter beads. length() counts beads. substring() takes beads from position 2 to 5.

String basics

String name = "Asha";
System.out.println(name.length());           // 4
System.out.println(name.toUpperCase());      // ASHA
System.out.println("Hello, " + name + "!");  // Hello, Asha!
System.out.println(name.charAt(0));          // A

Math — Math class

Java provides Math class with static methods — no need to create an object.

Math.max, Math.min, Math.sqrt, Math.pow, Math.abs, Math.round are used daily.

Real-life example: Math class is a pocket calculator built into Java — always ready, no install needed.

Math methods

System.out.println(Math.max(10, 20));    // 20
System.out.println(Math.min(10, 20));    // 10
System.out.println(Math.sqrt(16));       // 4.0
System.out.println(Math.pow(2, 3));      // 8.0
System.out.println(Math.abs(-7));        // 7
System.out.println(Math.round(3.6));     // 4