CODEWITHSUNDEEP
javaarraysarraylist
Altherat
Altherat

Reputation: 701

Is there a Java Class similar to ArrayList that can do this?

I have been running into this problem sometimes when programming.

Imagine I have a table of data with two columns. The first column has strings, the second column has integers.

I want to be able to store each row of the table into a dynamic array. So each element of the array needs to hold a string and an integer.

Previously, I have been accomplishing this by just splitting each column of the table into two separate ArrayLists and then when I want to add a row, I would call the add() method once on each ArrayList. To remove, I would call the remove(index) method once on each ArrayList at the same index.

But isn't there a better way? I know there are classes like HashMap but they don't allow duplicate keys. I am looking for something that allows duplicate entries.

I know that it's possible to do something like this:

ArrayList<Object[]> myArray = new ArrayList<Object[]>();
myArray.add(new Object[]{"string", 123});

I don't really want to have to cast into String and Integer every time I get an element out of the array but maybe this is the only way without creating my own? This looks more confusing to me and I'd prefer using two ArrayLists.

So is there any Java object like ArrayList where it would work like this:

ArrayList<String, Integer> myArray = new ArrayList<String, Integer>();
myArray.add("string", 123);

Upvotes: 3

Views: 2079

Answers (9)

jahroy
jahroy

Reputation: 22692

You should create a class (e.g. Foo) that contains an int and a String.

Then you can create an ArrayList of Foo objects.

List<Foo> fooList = new ArrayList<Foo>();

Upvotes: 2

Kumar Vivek Mitra
Kumar Vivek Mitra

Reputation: 33544

Use Map to solve this problem:

Map<String, Integer> map = new HashMap<String, Integer>();

Eg:

map.put("string", 123);

Upvotes: 0

Subhrajyoti Majumder
Subhrajyoti Majumder

Reputation: 41220

you can use google collection library Guava there is a Map called Multimap. It is collection similar to a Map, but which may associate multiple values with a single key. If you call put(K, V) twice, with the same key but different values, the multimap contains mappings from the key to both values.

Upvotes: 0

Sergey Passichenko
Sergey Passichenko

Reputation: 6930

Just create simple POJO class to hold row data. Don't forget about equals and hashCode and prefer immutable solution (without setters):

public class Pair {
    private String key;
    private Integer value;

    public Pair(String key, Integer value) {
        this.key = key;
        this.value = value;
    }

    public String getKey() {
        return key;
    }

    public Integer getValue() {
        return value;
    }

    // autogenerated

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof Pair)) return false;

        Pair pair = (Pair) o;

        if (key != null ? !key.equals(pair.key) : pair.key != null) return false;
        if (value != null ? !value.equals(pair.value) : pair.value != null) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = key != null ? key.hashCode() : 0;
        result = 31 * result + (value != null ? value.hashCode() : 0);
        return result;
    }
}

Usage:

    List<Pair> list = new ArrayList<Pair>();
    list.add(new Pair("string", 123));

Note: in other languages there are build-in solutions for it like case-classes and tuples in Scala.

Upvotes: 9

Naved
Naved

Reputation: 4128

Map is the option if you are sure that any one value among integer or string is unique. Then you can put that unique value as a key. If it is not true for your case, creating a simple POJO is best option for you. Infact, if in future, there a chance to come more values (columns) per row then also using a POJO will be less time consuming. You can define POJO like; 

public class Data {

 private int intValue;
 private String strValue;

 public int getIntValue() {
   return intValue;
 }

 public void setIntValue(int newInt) {
  this.intValue = newInt;
 }

 public String getStrValue() {
   return strValue;
 }

 public void setStrValue(String newStr) {
  this.strValue = newStr;
 }

And in the class you can use it like; 

ArrayList<Data> dataList = new ArrayList<Data>();  
Data data = new Data();  
data.setIntValue(123);  
data.setStrValue("string");  
dataList.add(data);

Upvotes: 3

maba
maba

Reputation: 48095

Create a Row class that holds the data.

package com.stackoverflow;

import java.util.ArrayList;
import java.util.List;

/**
 * @author maba, 2012-10-10
 */
public class Row {
    private int intValue;
    private String stringValue;

    public Row(String stringValue, int intValue) {
        this.intValue = intValue;
        this.stringValue = stringValue;
    }

    public int getIntValue() {
        return intValue;
    }

    public String getStringValue() {
        return stringValue;
    }

    public static void main(String[] args) {
        List<Row> rows = new ArrayList<Row>();
        rows.add(new Row("string", 123));
    }
}

Upvotes: 4

Grisha Weintraub
Grisha Weintraub

Reputation: 7986

You can create very simple object, like :

public class Row{
   private String strVal;
   private Integer intVal;

   public Row(String s, Integer i){
        strVal = s;
        intVal = i;
   }

   //getters and setters
}

Then use it as follows :

ArrayList<Row> myArray = new ArrayList<Row>();
myArray.add(new Row("string", 123));

Upvotes: 3

kosa
kosa

Reputation: 66657

HashMap my be the class you are looking for assuming "string" going to different for different values. Here is documentation on HashMap

Example:

HashMap<String, Integer> tempMap = new HashMap<String, Integer>();
tempMap.put("string", 124);

If you need to add more than one value, you may create HashMap<String, ArrayList> like that.

Upvotes: 0

MikeB
MikeB

Reputation: 2452

This is called a map my friend. It is similar to a dictionary in .net

http://docs.oracle.com/javase/6/docs/api/java/util/Map.html

Upvotes: 1

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