CODEWITHSUNDEEP
javaarrayssorting
edi233
edi233

Reputation: 3031

Java and operations on array

I have a problem with arrays in java. I have a array:

double[][] tab2 = {{318, 0.0825},
                  {321, 0.1131},
                  {309, 0.0283},
                  {319, 0.0830}};

and I need to change that array to:

double[][] tab2 = {{318, 0.0830},
                  {321, 0.0283},
                  {309, 0.1131},
                  {319, 0.0825}};

This is what i mean. I have four numbers. In this example 318, 321, 309 and 319. Every number is connected with another number, like 318 - 0.0825, 321 - 0.1131, etc. I need change value second values. When number which is connected with the biggest number should be connected with the smaller eg. 321 - 0.1131 should be 321 - 0.0283, 318 - 0.00830 should be 318 - 0.0825. It is possible to do this things?

Upvotes: 0

Views: 169

Answers (4)

GETah
GETah

Reputation: 21429

You can achieve this by:

HashMap<Integer,Double> mapValues = new HashMap<Integer,Double>();
// Insert keys and values into mapValues
Integer[] keys  = mapValues.KeySet().toArray(new Integer[]{});
Double[] values = mapValues.Values().toArray(new Double[]{});
Arrays.sort(keys,Collections.reverseOrder());
Arrays.sort(values);
HashMap<Integer,Double> resultMap = new HashMap<Integer,Double>();
for(int i=0; i<keys.length; i++){
   resultMap.put(keys[i], values[i]);
}

Upvotes: 0

Robin
Robin

Reputation: 36611

This will probably not be the most efficient solution, but it will work

double[][] tab2 = {{318, 0.0825},
              {321, 0.1131},
              {309, 0.0283},
              {319, 0.0830}};
List<Double> firstEntries = new ArrayList<Double>(  );
List<Double> secondEntries = new ArrayList<Double>(  );
for ( double[] doubles : tab2 ) {
  firstEntries.add( doubles[ 0 ] );
  secondEntries.add( doubles[ 1 ] );
}
Collections.sort( firstEntries );
Collections.sort( secondEntries );
Collections.reverse( secondEntries );
//now the lists contain the entries in the correct order
//if needed, they can be grouped again in an array
for ( int i = 0; i < tab2.length; i++ ) {
  double[] doubles = tab2[ i ];
  doubles[1] = secondEntries.get( firstEntries.indexOf( doubles[0] ) );
}

Upvotes: 0

Gnat
Gnat

Reputation: 2921

It would be easier to do this if the arrays were arranged in transposed form.

double[][] tab3 = {
    {318.0, 321.0, 309.0, 319.0},
    {0.0830, 0.1131, 0.0283, 0.0830}}

You can then sort the first array (tab3[0]) in ascending order and then the second array (tab3[1]) in descending order. Then all of the array indexes will line up and match the largest to the smallest. double[0][0] will be the biggest and double[1][0] will be the smallest, matching 309 and 0.1131 together.

double[][] tab3 = {
    {309.0, 318.0, 319.0, 321.0},
    {0.1131, 0.0830, 0.0830, 0.0283}}

Upvotes: 4

Selvakumar Ponnusamy
Selvakumar Ponnusamy

Reputation: 5543

You can use Map in this case, Specify first number as key and second number as value. Refer below document for more details about Map.

http://docs.oracle.com/javase/7/docs/api/java/util/Map.html

Upvotes: 1

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