直接上代碼
public class OrderAnnotationTest {
public static void main(String[] args) {
A a = new A();
B b = new B();
C c = new C();
List<Object> orderList = new ArrayList<>(3);
orderList.add(a);
orderList.add(b);
orderList.add(c);
orderList.sort(AnnotationAwareOrderComparator.INSTANCE);
System.out.println(orderList);
}
@Order(0)
static class A {
@Override
public String toString() {
return "A";
}
}
@Order(-1)
static class B {
@Override
public String toString() {
return "B";
}
}
@Order(2)
static class C {
@Override
public String toString() {
return "C";
}
}
}
結(jié)果如下：
[B, A, C]
原理解析：
AnnotationAwareOrderComparator繼承自OrderComparator,實(shí)際比較的方法如下
private int doCompare(@Nullable Object o1, @Nullable Object o2, @Nullable OrderSourceProvider sourceProvider) {
boolean p1 = (o1 instanceof PriorityOrdered);
boolean p2 = (o2 instanceof PriorityOrdered);
if (p1 && !p2) {
return -1;
}
else if (p2 && !p1) {
return 1;
}
int i1 = getOrder(o1, sourceProvider);
int i2 = getOrder(o2, sourceProvider);
return Integer.compare(i1, i2);
}
