#effectivejava

[asadmukhtarr]

Effective Java by Joshua Bloch is a definitive guide for Java developers who want to write efficient, maintainable, and robust code. Th

Effective Java by Joshua Bloch is a definitive guide for Java developers who want to write efficient, maintainable, and robust code. The third edition, updated for Java 7, 8, and 9, provides 90 best practices (or "items") that cover a wide range of topics, from language fundamentals to advanced techniques. Below is a step-by-step breakdown of the key outcomes and takeaways from the book:

[valladanger]

the bigger the haystack, the more useful it is to have a metal detector

J. Bloch @ Effective Java 2nd Ed

[valladanger]

the bigger the haystack, the more useful it is to have a metal detector

J. Bloch @ Effective Java 2nd Ed

[talatuyarer]

Why does Java's hashCode() in String use 31 as a multiplier?

The value 31 was chosen because it is an odd prime. If it were even and the multiplication overflowed, information would be lost, as multiplication by 2 is equivalent to shifting. The advantage of using a prime is less clear, but it is traditional. A nice property of 31 is that the multiplication can be replaced by a shift and a subtraction for better performance: 31 * i == (i << 5) - i. Modern VMs do this sort of optimization automatically.

(from Chapter 3, Item 9: Always override hashcode when you override equals, page 48, Joshua Bloch's Effective Java)

[mixaceh]

Effective Java實作Comparator - 就是愛Java

如果集合或陣列內的物件，有1個以上不同的排序邏輯時，那該如何處理呢？尤其是當已經實現了Comparable，又不能變動原本的邏輯時，Mix會採用Comparator來處理。

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[mixaceh]

Effective Java實作Comparable - 就是愛Java

當集合或陣列內的物件需要排序時，會利用Collections.sort或Arrays.sort來進行排序，通常會implement Comparable，來實現自定義排序，透過回傳值來表示排序的大小。

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[mixaceh]

Effective Java實作toString() - 就是愛Java

Object class中，也定義了toString()這個方法，因此所有的class也都繼承這個方法。預設是傳回這個物件完整類別名稱，後面接一個"@"，及一個不帶正副號的十六進制hash碼。

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[mixaceh]

Effective Java提升Code Coverage代碼涵蓋率 - 就是愛Java

雖然我們已經有了測試程式，但是如何得知是否已完整測試了主程式？，透過Code Coverage代碼涵蓋率，我們可以快速地得知，目前系統中，有多少程式中被測試過，不考量成本跟投資效益比，涵蓋率越高，代表系統如預期正常運作的面向也越廣泛。

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