Will the Guru

1. Reuse objects

• Rather than creating new objects that does the same job every time, reuse the single object by using static factory methods or immutable object.
  • For example, use Boolean.valueOf(String) which is a static factory method rather than Boolean(String).
  • Immutable objects like String can be reused any time. For example, use String s = "bikini"; rather than String s = new String("bikini");

• Reuse the expensive object by caching
  
  • String.matches() can degrade the performance as it uses Pattern instance just once and discards it which leaves it to the GC.
    
  • To improve the performance, create the Pattern instance from the class instantiating level by declaring it as static, and reuse whenever it’s required.

2. Adapter pattern

• Adapter is an object that delegates to a backing object, providing an alternative interface
  • keySet() of Map interface returns a Set view of the Map object, which returns the same Set instance per every call.
    

3. Prefer primitives to boxed primitives

• sum += i; would create Long instance every time. Changing the sum type from Long to long improves the performance much better.
  
• Long sum, long i =>
• long sum, long i =>
• Long sum , Long i =>

Check List

1. What is the difference between primitive type and boxed primitive type ?

• To Be Updated

2. Why is String type immutable ?

• Why is String Immutable?

Reference

• https://jyami.tistory.com/61