int i = 0;
for (Map.Entry<String,Integer> es : sortedMap.entrySet()){
if (i >= 10) {
break;
}
if (sortedMap.containsKey(es.getKey())){
System.out.println(es.getKey() + ":" + sortedMap.get(es.getKey()));
} else {
System.out.println("Key " + es.getKey() + " does not exist,yet...");
System.out.println("This does work: " + es.getKey() + ":" + es.getValue());
System.out.println("This does NOT work: " + es.getKey() + ":" + sortedMap.get(es.getKey()));
}
i++;
}
并获得以下结果：
SOAP:967
'excerpt'::679
'type'::679
Key 'author_url': does not exist,yet...
This does work: 'author_url'::679
This does NOT work: 'author_url'::null
'date'::679
Android:437
TLS:295
message:283
server:230
monthly:215
<<<<<<<<<<<<<<<<<<<<DUMPING MAP!
{SOAP=967,'excerpt':=679,'type':=679,'author_url':=679,'date':=679,Android=437,TLS=295,message=283,server=230,monthly=215...
我在前十名之后切断了地图,因为那里有更多的地图,但所有这些都是一个有价值的钥匙.
所以我的问题是这样的：当我使用密钥从TreeMap直接获取(key)时,为什么我得到null,但是EntrySet返回正确的键和值？
这是我的比较器,因为我在Integer上订购：
class ValueComparator implements Comparator<Object> {
Map<String,Integer> base;
public ValueComparator(Map<String,Integer> base) {
this.base = base;
}
public int compare(Object a,Object b) {
if ((Integer) base.get(a) < (Integer) base.get(b)) {
return 1;
} else if ((Integer) base.get(a) == (Integer) base.get(b)) {
return 0;
} else {
return -1;
}
}
}
TreeMap的构建如下：
ValueComparator bvc = new ValueComparator(allMatches); TreeMap<String,Integer> sortedMap = new TreeMap<String,Integer>(bvc); //Sort the HashMap sortedMap.putAll(allMatches);
allMatches是HashMap< String,Integer>
解决方法
请注意,根据javadocs：
The implementor must ensure that sgn(compare(x,y)) == -sgn(compare(y,
x)) for all x and y. (This implies that compare(x,y) must throw an
exception if and only if compare(y,x) throws an exception.)The implementor must also ensure that the relation is transitive:
((compare(x,y)>0) && (compare(y,z)>0)) implies compare(x,z)>0.Finally,the implementer must ensure that compare(x,y)==0 implies
that sgn(compare(x,z))==sgn(compare(y,z)) for all z.
如果您的比较器不应用这些规则 – 行为未定义,可能会显示奇怪的结果 – 如您所见.
编辑：[作为对编辑问题的回应]
您的隔离专区使用identity [operator ==]来检查两个整数.
请注意,Integer是一个对象 – 因此operator ==只有在它是同一个对象时才会返回true.
您应该使用equals()检查两个整数是否相同 – 甚至更好 – 使用Integer.compareTo()
