Finding the max min value in an array of primitives using Java

Question

It s trivial to write a function to determine the min max value in an array  such as               param chars     return the max value in the array of chars     private static int maxValue char   chars        int max   chars 0       for  int ktr   0  ktr  lt  chars length  ktr              if  chars ktr   gt  max                max   chars ktr                       return max      but isn t this already done somewhere

User · Answer

Here is a solution to get the max value in about 99% of runs (change the 0.01 to get a better result):

public static double getMax(double[] vals){
    final double[] max = {Double.NEGATIVE_INFINITY};

    IntStream.of(new Random().ints((int) Math.ceil(Math.log(0.01) / Math.log(1.0 - (1.0/vals.length))),0,vals.length).toArray())
            .forEach(r -> max[0] = (max[0] < vals[r])? vals[r]: max[0]);

    return max[0];
}

(Not completely serious)

User · Answer

You can simply use the new Java 8 Streams but you have to work with int   The stream method of the utility class Arrays gives you an IntStream on which you can use the min method  You can also do max  sum  average      The getAsInt method is used to get the value from the OptionalInt  import java util Arrays   public class Test       public static void main String   args           int   tab    12  1  21  8           int min   Arrays stream tab  min   getAsInt            int max   Arrays stream tab  max   getAsInt            System out println  Min       min           System out println  Max       max               UPDATE    If execution time is important and you want to go through the data only once you can use the summaryStatistics   method like this  import java util Arrays  import java util IntSummaryStatistics   public class SOTest       public static void main String   args           int   tab    12  1  21  8           IntSummaryStatistics stat   Arrays stream tab  summaryStatistics            int min   stat getMin            int max   stat getMax            System out println  Min       min           System out println  Max       max             This approach can give better performance than classical loop because the summaryStatistics method is a reduction operation and it allows parallelization

User · Answer

Example with float   public static float getMaxFloat float   data         float   copy   Arrays copyOf data  data length       Arrays sort copy       return copy data length - 1      public static float getMinFloat float   data         float   copy   Arrays copyOf data  data length       Arrays sort copy       return copy 0

User · Answer

import java util Random   public class Main    public static void main String   args       int a     new int  100      Random rnd   new Random          for  int i   0  i lt  a length  i              a i    rnd nextInt 99-0  0          System out println a i               int max   0                 for  int i   0  i  lt  a length  i              a i    max            for  int j   i 1  j lt a length  j                  if  a j   gt  max                   max   a j                                       System out println  Max element      max

User · Answer

By sorting the array  you get the first and last values for min   max  import java util Arrays   public class apples      public static void main String   args        int a      2 5 3 7 8       Arrays sort a        int min  a 0       System out println min        int max  a a length-1       System out println max               Although the sorting operation is more expensive than simply finding min max values with a simple loop  But when performance is not a concern  e g  small arrays  or your the cost is irrelevant for your application   it is a quite simple solution  Note  the array also gets modified after this

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int   arr    1  2  3        List lt Integer gt  list   Arrays stream arr  boxed   collect Collectors toList         int max    Collections max list       int i      if  max   gt  0            for  i   1  i  lt  Collections max list   i                  if   list contains i                     System out println i                   break                                  if i  max                System out println i 1                   else           System out println  quot 1 quot

User · Answer

Using Commons Lang  to convert    Collections  to min max   import java util Arrays  import java util Collections   import org apache commons lang ArrayUtils   public class MinMaxValue        public static void main String   args            char   a     3    5    1    4    2             List b   Arrays asList ArrayUtils toObject a             System out println Collections min b            System out println Collections max b             Note that Arrays asList   wraps the underlying array  so it should not be too memory intensive and it should not perform a copy on the elements of the array

User · Answer

I have a little helper class in all of my applications with methods like   public static double arrayMax double   arr        double max   Double NEGATIVE INFINITY       for double cur  arr          max   Math max max  cur        return max

User · Answer

Yes  it s done in the Collections class  Note that you will need to convert your primitive char array to a Character   manually   A short demo   import java util     public class Main        public static Character   convert char   chars            Character   copy   new Character chars length           for int i   0  i  lt  copy length  i                  copy i    Character valueOf chars i                      return copy             public static void main String   args            char   a     3    5    1    4    2            Character   b   convert a           System out println Collections max Arrays asList b

User · Answer

Pass the array to a method that sorts it with Arrays sort   so it only sorts the array the method is using then sets min to array 0  and max to array array length-1

User · Answer

The Google Guava library has min and max methods in its Chars  Ints  Longs  etc  classes   So you can simply use   Chars min myarray    No conversions are required and presumably it s efficiently implemented

User · Answer

Here s a utility class providing min max methods for primitive types  Primitives java int    numbers   10 1 8 7 6 5 2       int a Integer MAX VALUE      for int c numbers            a c lt a c a                         System out println  quot Lowest value is quot  a

User · Answer

public int getMin int   values           int ret   values 0           for int i   1  i  lt  values length  i                ret   Math min ret values i            return ret

User · Answer

A solution with reduce     int   array    23  3  56  97  42      directly print out Arrays stream array  reduce  x  y  - gt  x  gt  y   x   y  ifPresent System out  println       get the result as an int int res   Arrays stream array  reduce  x  y  - gt  x  gt  y   x   y  getAsInt    System out println res    gt  gt  97 97   In the code above  reduce   returns data in Optional format  which you can convert to int by getAsInt      If we want to compare the max value with a certain number  we can set a start value in reduce     int   array    23  3  56  97  42      e g   compare with 100 int max   Arrays stream array  reduce 100   x  y  - gt  x  gt  y   x   y   System out println max    gt  gt  100   In the code above  when reduce   with an identity  start value  as the first parameter  it returns data in the same format with the identity  With this property  we can apply this solution to other arrays   double   array    23 1  3  56 6  97  42   double max   Arrays stream array  reduce array 0    x  y  - gt  x  gt  y   x   y   System out println max    gt  gt  97 0

User · Answer

The basic way to get the min max value of an Array  If you need the unsorted array  you may create a copy or pass it to a method that returns the min or max  If not  sorted array is better since it performs faster in some cases   public class MinMaxValueOfArray       public static void main String   args            int   A    2  4  3  5  5           Arrays sort A           int min   A 0           int max   A A length -1           System out println  Min Value       min                   System out println  Max Value       max

User · Answer

You could easily do it with an IntStream and the max   method   Example  public static int maxValue final int   intArray      return IntStream range 0  intArray length  map i - gt  intArray i   max   getAsInt        Explanation   range 0  intArray length  - To get a stream with as many elements as present in the intArray  map i - gt  intArray i   - Map every element of the stream to an actual element of the intArray  max   - Get the maximum element of this stream as OptionalInt  getAsInt   - Unwrap the OptionalInt   You could also use here  orElse 0   just in case the OptionalInt is empty

[java] Finding the max/min value in an array of primitives using Java

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