What is the difference between Integer and int in Java?

Efficiency: int vs. Integer

From a performance standpoint, int generally outperforms Integer because of its raw, unencumbered nature. It’s especially true in contexts involving frequent mathematical operations. However, Integer provides object-like functionalities (for example: compareTo, toString, hashCode) that can be quite useful, especially when dealing with collections or null values.

Nullability: Exploring the Void

An Integer gives you the power to hold null values — a trait that serves a semantic purpose in many applications (denoting missing or optional data, for instance). But be aware of the dark side of Object realm: autounboxing a null value leads to NullPointerException.

Generics and Collections: Integer's Secret Powers

Integer is the undisputed choice for generics and collections, since they can't get enough of objects. Autoboxing makes it a breeze to convert int to Integer, reducing the need for manual object construction.

List<Integer> intList = new ArrayList<>(); // The List is dark and full of Integers
intList.add(42); // 42, autoboxing from int to Integer, hitchhiker approved
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Conversion: Playing Safe with Integer.valueOf()

Conversion from primitive int to Integer can be handled explicitly using the method Integer.valueOf(int). Want to make your code safer? Explicit conversion is the key!

Autoboxing: Java's Magic Trick

Java 5 introduced a magical act — autoboxing and unboxing. While it's great for convenience, remember: every magic trick has a price. The process can sometimes mask performance degradation.

Much More than Meets the Eye

Polymorphism Matters

Since Integer is a child of the Object superclass, it can go wherever Object goes. This enables polymorphic behavior, which int can't enjoy.

Dealing with Strings

The Integer.parseInt method converts a string to primitive int, while Integer.valueOf(String) gives you an Integer. This can be critical when dealing with numeric values encapsulated in string literal.

Memory: Closer Look

Follow the rabbit hole deeper: int stores its raw, unadorned numeric beauty directly in memory, while Integer is a classier creature with a refined Object taste, holding the int value in its field and sipping a tad more memory.

Common Pitfalls: To Watch Out For

The ease of autoboxing can sometimes dupe developers into overusing it, leading to hidden boxing conversions and potential performance degradation due to garbage collection overhead. Beware!