第 61 条：基本类型优先于装箱类型

基本类型优先于装箱类型.jpeg

// Broken comparator - can you spot the flaw?
Comparator<Integer> naturalOrder = (i, j) -> (i < j) ? -1 : (i == j ? 0 : 1);

Comparator<Integer> naturalOrder = (iBoxed, jBoxed) -> {
    int i = iBoxed, j = jBoxed; // Auto-unboxing
    return i < j ? -1 : (i == j ? 0 : 1);
};

public class Unbelievable {
    static Integer i;
    public static void main(String[] args) {
        if (i == 42)
            System.out.println("Unbelievable");
    }
}

// Hideously slow program! Can you spot the object creation?
public static void main(String[] args) {
    Long sum = 0L;
    for (long i = 0; i < Integer.MAX_VALUE; i++) {
        sum += i;
    }
    System.out.println(sum);
}