被一個詭異的bug折騰了半天,當找到原因時哭笑不得。先看如下代碼,大家分析一下打出來的會是什麼:
public class TestDebug {
private static HashMap<String, BleDeviceProp> mPropCache = new HashMap<String, BleDeviceProp>();
public static void main(String[] args) {
// TODO Auto-generated method stub
BleDeviceProp prop = new BleDeviceProp("one");
prop.name = "apple";
mPropCache.put(prop.mac, prop);
setPropName(prop.mac, "orange");
System.out.println(prop.name);
}
private static class BleDeviceProp {
private String mac;
private String name;
BleDeviceProp(String mac) {
this.mac = mac;
}
}
private static void setPropName(String mac, String name) {
setProp(mac, new PropSetter("name") {
@Override
public boolean setProp(BleDeviceProp prop) {
// TODO Auto-generated method stub
prop.name = name;
return false;
}
});
}
private static void setProp(String mac, PropSetter setter) {
BleDeviceProp prop = mPropCache.get(mac);
if (prop == null) {
prop = new BleDeviceProp("");
mPropCache.put(mac, prop);
}
setter.setProp(prop);
}
private interface IPropSetter {
boolean setProp(BleDeviceProp prop);
}
private static abstract class PropSetter implements IPropSetter {
String name;
PropSetter(String name) {
this.name = name;
}
}
}
按理說這裏給name設置成orange,打出來的應該是orange纔對,但事實上打出來的是name。很奇怪吧,原因在哪裏?
原因在於這個PropSetter內部也有一個成員變量爲name,沒有加修飾符,所以默認爲protected。在回調裏,這個name的優先級高於setPropName的參數name,所以被搶佔了。解決辦法很簡單,給PropSetter的name改成private的,或者乾脆別讓他們名稱衝突就可以了。