How to iterate through objects in Hashmap

问题

I am having

Map<String, List<Attribute>> binList = new HashMap<String, List<Attribute>>();

I want to iterate through each values in list By doing this I am able to get the key and its entire values.But how to get each single value for a key.

BinList {3=[index=0 {from=1.3,to=2.42}, index=1 {from=2.42,to=3.54}, index=2 {from=3.54,to=4.66}, index=3 {from=4.66,to=5.78}, index=4 {from=5.78,to=6.9}], 2=[index=0 {from=2.3,to=2.76}, index=1 {from=2.76,to=3.2199999999999998}, index=2 {from=3.2199999999999998,to=3.6799999999999997}, index=3 {from=3.6799999999999997,to=4.14}, index=4 {from=4.14,to=4.6}], 1=[index=0 {from=4.3,to=5.02}, index=1 {from=5.02,to=5.739999999999999}, index=2 {from=5.739999999999999,to=6.459999999999999}, index=3 {from=6.459999999999999,to=7.179999999999999}, index=4 {from=7.179999999999999,to=7.899999999999999}], 4=[index=0 {from=0.3,to=0.76}, index=1 {from=0.76,to=1.2200000000000002}, index=2 {from=1.2200000000000002,to=1.6800000000000002}, index=3 {from=1.6800000000000002,to=2.14}, index=4 {from=2.14,to=2.6}]}



Map<String, List<Attribute>> binList = new HashMap<String, List<Attribute>>();
System.out.println("BinList "+binList);
//Iterating binList
while (it.hasNext()) {
    Map.Entry pairs = (Map.Entry)it.next();
    System.out.println("->>>>"+pairs.getKey() + " = " + pairs.getValue());
    }

OUTPUT

->>>>3 = [index=0 {from=1.3,to=2.42}, index=1 {from=2.42,to=3.54}, index=2 {from=3.54,to=4.66}, index=3 {from=4.66,to=5.78}, index=4 {from=5.78,to=6.9}]
->>>>2 = [index=0 {from=2.3,to=2.76}, index=1 {from=2.76,to=3.2199999999999998}, index=2 {from=3.2199999999999998,to=3.6799999999999997}, index=3 {from=3.6799999999999997,to=4.14}, index=4 {from=4.14,to=4.6}]
->>>>1 = [index=0 {from=4.3,to=5.02}, index=1 {from=5.02,to=5.739999999999999}, index=2 {from=5.739999999999999,to=6.459999999999999}, index=3 {from=6.459999999999999,to=7.179999999999999}, index=4 {from=7.179999999999999,to=7.899999999999999}]
->>>>4 = [index=0 {from=0.3,to=0.76}, index=1 {from=0.76,to=1.2200000000000002}, index=2 {from=1.2200000000000002,to=1.6800000000000002}, index=3 {from=1.6800000000000002,to=2.14}, index=4 {from=2.14,to=2.6}]

How to iterate through values

id =3
   index=0 {from=1.3,to=2.42}
   index=1 {from=2.42,to=3.54}
.
.

回答1:

You have a Map that contains values that are instances of List<Attribute>.

If you want to iterate though those lists and display their contents... you'd need to iterate through those lists;

for (Map.Entry<String, List<Attribute>> entry : binList.entrySet())
{
    System.out.println("Key: " + entry.getKey());

    // Each value is a List<Attribute>, so you can iterate though that as well
    for (Attribute a : entry.getValue())
    {
        // This assumes Attribute.toString() prints something useful 
        System.out.println("Attribute: " + a);
    }
}

Edit to add: You show an Iterator in your example, and you're using raw types instead of generics. The above does away with the Iterator but presumably this is the correct version of what you were trying to do using Iterators. The "for-each" loops shown above are equivalent:

Iterator<Map.Entry<String, List<Attribute>>> it = binList.entrySet().iterator();
while (it.hasNext())
{
    Map.Entry<String, List<Attribute>> entry = it.next();
    System.out.println("Key: " + entry.getKey());

    // Each value is a List<Attribute>, so you can iterate though that as well
    Iterator<Attribute> it2 = entry.getValue().iterator();

    while (it2.hasNext())
    {
        Attribute a = it2.next();
        // This assumes Attribute.toString() prints something useful 
        System.out.println("Attribute: " + a);
    }
}

回答2:

try with foreach style in java

for (String entryKey:binList.keySet()){
    for (List<Attribute> attribute:binList.get(entryKey)){
        attribute.from
        attribute.to
    }
}

来源：https://stackoverflow.com/questions/21793275/how-to-iterate-through-objects-in-hashmap

标签

java

list

hashmap