Refactoring Java Static to Instance Based | Generated by AI

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Question: How can I refactor this Java code to avoid using static methods and instead use an instance of the Main class?

Answer: To refactor your code to be instance-based, you should move the BufferedReader and PrintWriter into instance fields and call the solve() method on a new instance of Main created inside the main method.

Here is the updated code:

package com.lzw.solutions.codeforces.p2190B1;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;

public class Main {
    // Instance fields instead of static fields
    private final BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    private final PrintWriter out = new PrintWriter(System.out, true);

    // Instance method (no 'static' keyword)
    private void solve() throws IOException {
        String line = in.readLine();
        if (line == null) return;
        
        int t = Integer.parseInt(line.trim());
        while (t-- > 0) {
            int n = Integer.parseInt(in.readLine().trim());
            String s = in.readLine();
            // Using standard if-check or logging is often preferred over assert 
            // in production, but keeping it per your logic:
            assert (s.length() == n);
            out.println(s);
        }
    }

    public static void main(String[] args) {
        try {
            // Create an instance and call the instance method
            new Main().run();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // Helper to manage the lifecycle of the instance
    private void run() throws IOException {
        try {
            solve();
        } finally {
            out.close();
            in.close();
        }
    }
}

Key Changes Made:

• Removed static: The fields in and out and the method solve() no longer use the static modifier. They now belong to a specific instance of the class.
• Object Instantiation: In the main method, new Main().run() is used to jump from the static context into the instance context.
• Resource Management: Added a run() method with a finally block to ensure that your PrintWriter and BufferedReader are closed properly, even if an exception occurs during execution.

Would you like me to show you how to implement a faster custom Scanner class within this instance-based structure?

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