Develop Reference

How to SUM duplicate key values in LinkedHashMap?

I have a LinkedHashMap where I have two duplicate keys with their correspondent values, I need to know how to SUM those values into one key. Currently he eliminates the old duplicated value and put the new one
This is my Map
static Map<String, Double> costByDuration = new LinkedHashMap<>();
This is where I put the values ( call_from can be 912345678 and have a value of 10, and then another call from 912345678 and have a value of 20), then I want 912345678 to have a value of 30 instead of keeping only one.
costByDuration.put(call_from, toPay);

I'd create a method as follows:
public void put(String key, Double value){
costByDuration.merge(key,value , Double::sum);
}
then the use case would be:
put(call_from, toPay);
put(anotherKey, anotherValue);
...
...
This solution internally uses the merge method which basically says if the specified key is not already associated with a value or is associated with null, associates it with the given non-null value. Otherwise, replaces the associated value with the results of the given remapping function.

You'll have to check first whether your value is already in the map.
Double existingValue = costByDuration.get(callFrom);
if (existingValue != null) {
costByDuration.put(callFrom, existingValue + toPay);
} else {
costByDuration.put(callFrom, toPay);
}
Incidentally, it's a bad idea to use a Double to store an amount of money, if you want your arithmetic operations to give you the correct answer. I strongly recommend using BigDecimal in place of Double.

Use merge function:
costByDuration.merge(call_from, toPay, (oldPay, toPay) -> oldPay + toPay);

Try this using containsKey method :
static Map<String, Double> costByDuration = new LinkedHashMap<>();
if(costByDuration.containsKey(call_from) {
costByDuration.put(call_from, map.get(call_from) + to_Pay);
} else {
costByDuration.put(call_from, to_Pay);
}

How can I add a string one at a time to a HashMap<Integer, List<String>>?

This function loops through a dictionary (allWords) and uses the
getKey function to generate a key. wordListMap is a HashMap> so I need to loop through and put the key and and a List. If there is not a list I put one if there is I just need to append the next dictionary word. This is where I need help. I just can't figure out the syntax to simply append the next word to the list that is already there. Any Help would be appreciated.
public static void constructWordListMap() {
wordListMap = new HashMap<>();
for (String w : allWords) {
int key = getKey(w);
if (isValidWord(w) && !wordListMap.containsKey(key)) {
List list = new ArrayList();
list.add(w);
wordListMap.put(key, list);
} else if (isValidWord(w) && wordListMap.containsKey(key)) {
wordListMap.put(key, wordListMap.get(key).add(w));
}
}
}

map.get(key).add(value)
Simple as that.

So I've gathered that you want to, given HashMap<Integer, List<String>>, you'd like to:
create a List object
add String objects to said List
add that List object as a value to be paired with a previously generated key (type Integer)
To do so, you'd want to first generate the key
Integer myKey = getKey(w);
Then, you'd enter a loop and add to a List object
List<String> myList = new List<String>;
for(int i = 0; i < intendedListLength; i++) {
String myEntry = //wherever you get your string from
myList.add(myEntry);
}
Lastly, you'd add the List to the HashMap
myHash.put(myKey, myList);
Leave any questions in the comments.

else if (isValidWord(w) && wordListMap.containsKey(key)) {
wordListMap.put(key, wordListMap.get(key).add(w));
}
If you want to add a new value to your list, you need to retrieve that list first. In the code above, you are putting the return value of add into the table (which is a boolean), and that is not what you want.
Instead, you will want to do as Paul said:
else if (isValidWord(w) && wordListMap.containsKey(key)) {
wordListMap.get(key).add(w);
}
The reason this works is because you already added an ArrayList to the table earlier. Here, you are getting that ArrayList, and adding a new value to it.

Check value inside Map

I have a Map where I save values with the form NAME-GROUP.
Before doing some operations, I need to know if the Map contains a specific group,
for example: I need to check for values containing group1 like Mark-group1.
I'm trying to get it this way:
if (checkList.containsValue(group1)) {
exists = true;
}
I can't provide the name when searching because there could be diferent names with the same group.
But it isn't finding the value, as seems that this function just looks for the entire value string and not only for part of it.
So, there would be any way of achieving this, or would I need to change the way I'm focusing my code.
Update--
This is the looking of my Map:
Map<Integer, String> checkList = new HashMap<Integer, String>();
I load some values from a database and I set them into the Map:
if (c.moveToFirst()) {
int checkKey = 0;
do {
checkKey++;
checkList.put(checkKey, c.getString(c.getColumnIndex(TravelOrder.RELATION)));
}while(c.moveToNext());
}
The relation column, has values like: mark-group1, jerry-group1, lewis-group2, etc...
So, the Map will have a structure like [1, mark-group1], etc...
What I need is to check if there is any value inside the map that contains the string group1 for example, I don't care about the name, I just need to know if that group exists there.

If you want to check any value contain your string as a substring you have to do the following:
for (String value : yourMap.values()) {
if (value.contains(subString)) {
return true;
}
}
return false;
By the way if your values in the map are really have two different parts, i suggest to store them in a structure with two fields, so they can be easily searched.

Arraylist - String/Double

I am taking a basic objects first with java class, i don't know much yet and need a little help ..
I need to assign these values to an arraylist but also need to allow the user to choose a health option based on a string that will then output the value related to the option..
double [] healthBenDesig = new double [5];
double [] healthBenDesig = {0.00, 311.87, 592.56, 717.30, 882.60};
Strings I want to assign are:
none = 0.00
employeeOnly = 311.87
spouse = 592.56
children = 717.30
kids = 882.60
Ultimately, I want the user to input for example "none" and the output will relate none to the value held in the arraylist [0] slot and return that value. Is this possible? Or is there an easier way I am overlooking?
if anyone could help me out I would really appreciate it :)
Thanks

Yes. This is possible with HashMap.
HashMap<String,Double> healthMap = new HashMap<String,Double>();
healthMap.put("none",0.00);
healthMap.put("employeeOnly",311.87);
healthMap.put("spouse",592.56);
healthMap.put("children",717.30);
healthMap.put("kids",882.60);
Now, when user enters none then use get() method on healthMap to get the value.
For safety check that key exists in map using containsKey() method.
if(healthMap.containsKey("none")) {
Double healthVal = healthMap.get("none"); //it will return Double value
} else {
//show you have entered wrong input
}
See also
HashMap oracle docs

Best solution is Map<String, Double>.
Map<String,Double> map=new HashMap<>();
map.put("none",0.0);
Now when you want the value for "none" you can use get() method
map.get("none") // will return 0.0

Here's something for you to get started with since it's the assignment:
Create a Map<String, Double> that holds the number and string as key/value pair.
Store the above values into the map
When a user enters the input, capture it using Scanner
Do something like this.
if(map.containsKey(input)) {
value = map.get(input);
}

Use Map Inteface
Map<String, Double> healthBenDesig =new HashMap<String, Double>();
healthBenDesig.put("none", 0.00);
healthBenDesig.put("employeeOnly", 311.87);
healthBenDesig.put("spouse", 592.56);
healthBenDesig.put("children", 717.30);
healthBenDesig.put("kids", 882.60);
System.out.println(healthBenDesig);
OutPut
{
none = 0.0,
spouse = 592.56,
children = 717.3,
kids = 882.6,
employeeOnly = 311.87
}

Get key from a HashMap using the value [duplicate]

This question already has answers here:
Java Hashmap: How to get key from value?
(39 answers)
Closed 5 years ago.
I want to get the key of a HashMap using the value.
hashmap = new HashMap<String, Object>();
haspmap.put("one", 100);
haspmap.put("two", 200);
Which means i want a function that will take the value 100 and will return the string one.
It seems that there are a lot of questions here asking the same thing but they don't work for me.
Maybe because i am new with java.
How to do it?

The put method in HashMap is defined like this:
Object put(Object key, Object value)
key is the first parameter, so in your put, "one" is the key. You can't easily look up by value in a HashMap, if you really want to do that, it would be a linear search done by calling entrySet(), like this:
for (Map.Entry<Object, Object> e : hashmap.entrySet()) {
Object key = e.getKey();
Object value = e.getValue();
}
However, that's O(n) and kind of defeats the purpose of using a HashMap unless you only need to do it rarely. If you really want to be able to look up by key or value frequently, core Java doesn't have anything for you, but something like BiMap from the Google Collections is what you want.

We can get KEY from VALUE. Below is a sample code_
public class Main {
public static void main(String[] args) {
Map map = new HashMap();
map.put("key_1","one");
map.put("key_2","two");
map.put("key_3","three");
map.put("key_4","four");
System.out.println(getKeyFromValue(map,"four"));
}
public static Object getKeyFromValue(Map hm, Object value) {
for (Object o : hm.keySet()) {
if (hm.get(o).equals(value)) {
return o;
}
}
return null;
}
}
I hope this will help everyone.

If you need only that, simply use put(100, "one"). Note that the key is the first argument, and the value is the 2nd.
If you need to be able to get by both the key and the value, use BiMap (from guava)

You have it reversed. The 100 should be the first parameter (it's the key) and the "one" should be the second parameter (it's the value).
Read the javadoc for HashMap and that might help you: HashMap
To get the value, use hashmap.get(100).

You mixed the keys and the values.
Hashmap <Integer,String> hashmap = new HashMap<Integer, String>();
hashmap.put(100, "one");
hashmap.put(200, "two");
Afterwards a
hashmap.get(100);
will give you "one"

if you what to obtain "ONE" by giving in 100 then
initialize hash map by
hashmap = new HashMap<Object,String>();
haspmap.put(100,"one");
and retrieve value by
hashMap.get(100)
hope that helps.

public class Class1 {
private String extref="MY";
public String getExtref() {
return extref;
}
public String setExtref(String extref) {
return this.extref = extref;
}
public static void main(String[] args) {
Class1 obj=new Class1();
String value=obj.setExtref("AFF");
int returnedValue=getMethod(value);
System.out.println(returnedValue);
}
/**
* #param value
* #return
*/
private static int getMethod(String value) {
HashMap<Integer, String> hashmap1 = new HashMap<Integer, String>();
hashmap1.put(1,"MY");
hashmap1.put(2,"AFF");
if (hashmap1.containsValue(value))
{
for (Map.Entry<Integer,String> e : hashmap1.entrySet()) {
Integer key = e.getKey();
Object value2 = e.getValue();
if ((value2.toString()).equalsIgnoreCase(value))
{
return key;
}
}
}
return 0;
}
}

If you are not bound to use Hashmap, I would advise to use pair< T,T >.
The individual elements can be accessed by first and second calls.
Have a look at this http://www.cplusplus.com/reference/utility/pair/
I used it here : http://codeforces.com/contest/507/submission/9531943