Number Class

Number Class

1. What It Is (beginner)

Number = abstract parent of all numeric wrappers (Integer, Double, Long, ...). Lets you treat any number uniformly: pass Integer or Double where Number expected, then ask .intValue() / .doubleValue().

Number (abstract)
├── Integer, Long, Short, Byte (integers)
└── Double, Float (decimals) + BigInteger/BigDecimal

4. Traps

• Number is abstract: new Number() ERROR (use concrete Integer etc.).
• .intValue() on Double(3.99) cuts → 3 (narrowing!).
• instanceof to check kind: if (n instanceof Integer) before int-only ops.

5. Exam Points

• Hierarchy + doubleValue program — 3-5 marks, frequent.
• Abstract (no new) + conversion cut — 2-3 marks.