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Java 1.2

A comprehensive guide to all Java 1.2 concepts with practical examples for interview preparation.

Table of Contents

  1. Collections Framework
  2. Swing GUI Framework
  3. Strictfp Keyword
  4. Java Plug-in
  5. Common Interview Questions

1. Collections Framework

Java 1.2 introduced the Collections Framework, providing a unified architecture for representing and manipulating collections.

Overview

The Collections Framework provides implementations of data structures like lists, sets, and maps.

Core Interfaces

import java.util.*;

// List - Ordered collection
List<String> list = new ArrayList<>();
list.add("Java");
list.add("Python");
list.add("C++");

// Set - No duplicates
Set<Integer> set = new HashSet<>();
set.add(1);
set.add(2);
set.add(1); // Duplicate, ignored

// Map - Key-value pairs
Map<String, Integer> map = new HashMap<>();
map.put("Java", 1995);
map.put("Python", 1991);

Key Classes

  • ArrayList: Dynamic array implementation
  • LinkedList: Doubly-linked list
  • HashSet: Hash table-based set
  • TreeSet: Sorted set
  • HashMap: Hash table-based map
  • TreeMap: Sorted map

Benefits

  • Unified API
  • Reusable data structures
  • Type-safe collections
  • High performance
  • Standard implementations

See CollectionsFrameworkExample.java for complete example.

2. Swing GUI Framework

Swing provides a rich set of GUI components, replacing AWT for most GUI applications.

Overview

Swing is built on AWT but provides lightweight, platform-independent components.

Basic Swing Application

import javax.swing.*;

public class SwingExample extends JFrame {
    public SwingExample() {
        setTitle("Swing Example");
        setSize(400, 300);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        JButton button = new JButton("Click Me");
        JLabel label = new JLabel("Hello Swing");
        
        setLayout(new FlowLayout());
        add(label);
        add(button);
        
        setVisible(true);
    }
}

Key Features

  • Lightweight components
  • Pluggable look and feel
  • Rich component set
  • Better than AWT
  • MVC architecture

See SwingExample.java for complete example.

3. Strictfp Keyword

The strictfp keyword ensures consistent floating-point calculations across platforms.

Overview

strictfp guarantees that floating-point calculations produce the same results on all platforms.

Usage

strictfp class Calculator {
    strictfp double calculate(double a, double b) {
        return a * b / 3.14;
    }
}

Key Features

  • Platform-independent floating-point
  • Consistent results
  • IEEE 754 compliance
  • Can be applied to classes, interfaces, and methods

See StrictfpExample.java for complete example.

4. Java Plug-in

Java Plug-in allows applets to run in web browsers with better control.

Overview

Java Plug-in provides a way to run Java applets in browsers with improved security and performance.

Benefits

  • Better applet execution
  • Improved security
  • Better performance
  • Cross-browser support

Note: Java Plug-in and applets are deprecated in modern Java.

5. Common Interview Questions

Q1: What is the Collections Framework?

A: Unified architecture for collections:

  • Core interfaces: List, Set, Map
  • Implementations: ArrayList, HashSet, HashMap
  • Algorithms: Sorting, searching
  • Type-safe collections

Q2: What is the difference between ArrayList and LinkedList?

A:

  • ArrayList: Array-based, fast random access, slower insertions
  • LinkedList: Node-based, slow random access, fast insertions
  • Use ArrayList for frequent access
  • Use LinkedList for frequent insertions/deletions

Q3: What is Swing?

A: GUI framework:

  • Lightweight components
  • Platform-independent
  • Rich component set
  • Better than AWT
  • Pluggable look and feel

Q4: What is strictfp?

A: Keyword for consistent floating-point:

  • Ensures same results on all platforms
  • IEEE 754 compliance
  • Can be applied to classes, interfaces, methods

Q5: What is the difference between Set and List?

A:

  • Set: No duplicates, unordered (HashSet) or sorted (TreeSet)
  • List: Allows duplicates, maintains insertion order
  • Set for unique elements
  • List for ordered collections with duplicates

Last Updated: 2025
Version: 1.0

This guide covers the features of Java 1.2, released on December 8, 1998.