自动拆装箱与遍历

一、实例
源码：
List<Integer> list = Arrays.asList(1, 2);
int sum = 0;
for (int i : list) {
    sum += i;
}
System.out.println(sum);

编译后：
List<Integer> list = Arrays.asList(
    new Integer[] { Integer.valueOf(1), Integer.valueOf(2) });
int sum = 0;
for (Iterator localIterator = list.iterator(); localIterator.hasNext(); ) {
    int i = ((Integer)localIterator.next()).intValue();
    sum += i;
}
System.out.println(sum);

二、陷阱（源码）
Integer a = 1;
Integer b = 2;
Integer c = 3;
Integer d = 3;
Integer e = 321;
Integer f = 321;
Long g = 3L;
System.out.println(c == d);
System.out.println(e == f);
System.out.println(c == (a+b));
System.out.println(c.equals(a+b));
System.out.println(g == (a+b));
System.out.println(g.equals(c));

陷阱（编译后）
Integer a = Integer.valueOf(1);
Integer b = Integer.valueOf(2);
Integer c = Integer.valueOf(3);
Integer d = Integer.valueOf(3);
Integer e = Integer.valueOf(321);
Integer f = Integer.valueOf(321);
Long g = Long.valueOf(3L);
System.out.println(c == d);
System.out.println(e == f);
System.out.println(c.intValue() == a.intValue() + b.intValue());
System.out.println(c.equals(Integer.valueOf(a.intValue() + b.intValue())));
System.out.println(g.longValue() == a.intValue() + b.intValue());
System.out.println(g.equals(c));

来源：oschina

链接：https://my.oschina.net/u/3989883/blog/4740525