为什么Java Map不起作用？函数 .put() 不插入值，只插入键

Question

当我尝试插入与其键相关的值时，该值不会插入到映射中。它看起来像是"；ids"；它没有任何价值，但它确实有。

Map<String, Vector<String>> graph = new HashMap<String, Vector<String>>();
ArrayList<String[]> words = new ArrayList<String[]>();
Vector<String> ids = new Vector<String>();
String[] id = null;

Scanner scanner = new Scanner(new FileReader(fInName));
while (scanner.hasNextLine()) {
words.add(scanner.nextLine().split("\s+"));
}

for(int i = 0; i < words.size(); i++) {
id = words.get(i)[1].split("[,]", 0);
for(int j = 0; j < id.length; j++) {
ids.add(j, id[j]);
}
graph.put(words.get(i)[0], ids);
id = null;
ids.clear();            
}

for (Map.Entry<String, Vector<String>> entry : graph.entrySet()) {
System.out.println("Key = " + entry.getKey() +
", Value = " + entry.getValue());
}

Answer 1

put((函数通过引用工作。所以

put (key, ids)

存储对运行clear((函数的同一个id对象的引用(内存指针(。尝试"清理"内存是值得称赞的，但在这种情况下，你是在自食其果。你想要的是类似的东西

Map<String, Vector<String>> graph = new HashMap<String, Vector<String>>();
ArrayList<String[]> words = new ArrayList<String[]>();
Vector<String> ids;
String[] id = null;
Scanner scanner = new Scanner(new FileReader(fInName));
while (scanner.hasNextLine()) {
words.add(scanner.nextLine().split("\s+"));
}
for(int i = 0; i < words.size(); i++) {
id = words.get(i)[1].split("[,]", 0);
ids = new Vector<String>();
for(int j = 0; j < id.length; j++) {
ids.add(j, id[j]);
}
graph.put(words.get(i)[0], ids);        
}