Java漫谈-Long判等

Long判等源码

    public boolean equals(Object obj) {
        if (obj instanceof Long) {
            return value == ((Long)obj).longValue();
        }
        return false;
    }

可见Long类型的判等本身就是对值的判等，故不需要对Long做手动拆箱（即b.longValue()）操作：

Long a = 1L;
Long b = 3L;
a.equals(b); //这样既可
a.equals(b.longValue()); //无需这样

list.contains(o)源码

 public boolean contains(Object o) {
    return indexOf(o) >= 0;
 }
public int indexOf(Object o) {
if (o == null) {
for (int i = 0; i < size; i++)
if (elementData[i]==null)
return i;
} else {
for (int i = 0; i < size; i++)
if (o.equals(elementData[i]))
return i;
}
return -1;
}