Question

I need your help in JAVA (with some sample code if possible) regarding to the following scenario:
I have a list with a classes object and want to check if one object property has duplicates then
keep one of them and add others amounts with the kept one’s amount. For example:

I have this class:

class Salary {
    String names;
    Double amount;
}

and the list say salary_list contains the following elements in it(for example):

[jony,john   300.96]
[fuse,norvi,newby  1000.55]
[john,jony  22.6]
[richard,ravi,navin  55.6]
[fuse,norvi,newby  200.6]
... ... ...

So what is my expected output is the same input list with the following revised result:

[jony,john  323.56]
[fuse,norvi,newby  1201.15]
[richard,ravi,navin  55.6]

N.B: order in names is not important so not the order of the elements after the duplicate elimination.
I am not good at english as well as in Java. So forgive me if any mistakes there.

Thanks in advance.

Answer 1

Enhance your Salary class as follows:

class Salary {
    String names;
    Double amount;
    private String sortedNames = null;

    @Override
    public boolean equals(Object o)
    {
        if (o == null || ! (o instanceof Salary)) return false;
        Salary othr = (Salary) o;
        String thisNames = this.getSortedNames();
        String othrNames = othr.getSortedNames();
        return thisNames.equals(othrNames);
    }

    @Override 
    public int hashCode()
    {
        return getSortedNames().hashCode();
    }

    public String getSortedNames()
    {
        if (this.sortedNames == null)
        {
            String[] nameArr = this.names.split(",");
            Arrays.sort(nameArr);
            StringBuilder buf = new StringBuilder();
            for (String n : nameArr)
                buf.append(",").append(n);
            this.sortedNames = buf.substring(buf.length()==0?0:1);
        }

        return this.sortedNames; 
    }
}

This assumes that Salary is immutable (that is, after it’s created the values of names and amount won’t change. You could then use this with a hash map to add up all the amounts having the same names.

    Map<String,Salary>  map  = new HashMap<String,Salary>();
    for (Salary s : list)
    {
        Salary e = map.get(s.getSortedNames());
        if (e == null)
            map.put(s.getSortedNames(), s);
        else
            e.amount += s.amount;
    }

At this point the map contains all unique Salary objects with the total amount for each.