Concurrency Best Practices

Writing robust concurrent applications requires adopting defensive programming techniques. Immutable data, minimizing lock scopes, and preferring modern concurrency collections are the foundations of thread safety.

Key Concurrency Principles

• Immutability: Immutable objects (like Java Record classes or final-field classes) have no mutable state. They are inherently thread-safe and can be shared freely without locks.
• Concurrent Collections: Avoid wrapping legacy collections in Collections.synchronizedMap() (which locks the entire collection). Use ConcurrentHashMap (which locks on bucket segments, enabling parallel reads/writes) and CopyOnWriteArrayList (safe for read-heavy operations).
• Minimize Lock Scope: Never hold a lock during expensive operations like network requests, database transactions, or file I/O to prevent system bottlenecks.
• Prefer JUC Utilities: Use java.util.concurrent tools (like thread pools, locks, atomics) instead of low-level wait()/notify().

Code Walkthrough

This class demonstrates implementing an immutable, thread-safe configuration holder.

public final class SystemConfig {
    private final String dbUrl;
    private final int maxConnections;
public SystemConfig(String dbUrl, int maxConnections) {
        this.dbUrl = dbUrl;
        this.maxConnections = maxConnections;
    }
// No setters! Only getters return copy or primitive.
    public String getDbUrl() { return dbUrl; }
    public int getMaxConnections() { return maxConnections; }
}

Interview-Relevant Information