JAVA TUTORIALS - Java - Arrays

Java - Arrays

The Arrays Class:

SN	Methods with Description
1	public static int binarySearch(Object[] a, Object key) Searches the specified array of Object ( Byte, Int , double, etc.) for the specified value using the binary search algorithm. The array must be sorted prior to making this call. This returns index of the search key, if it is contained in the list; otherwise, (-(insertion point + 1).
2	public static boolean equals(long[] a, long[] a2) Returns true if the two specified arrays of longs are equal to one another. Two arrays are considered equal if both arrays contain the same number of elements, and all corresponding pairs of elements in the two arrays are equal. This returns true if the two arrays are equal. Same method could be used by all other primitive data types (Byte, short, Int, etc.)
3	public static void fill(int[] a, int val) Assigns the specified int value to each element of the specified array of ints. Same method could be used by all other primitive data types (Byte, short, Int etc.)
4	public static void sort(Object[] a) Sorts the specified array of objects into ascending order, according to the natural ordering of its elements. Same method could be used by all other primitive data types ( Byte, short, Int, etc.)

Declaring Array Variables:

dataType[] arrayRefVar;   // preferred way.

or

dataType arrayRefVar[];  //  works but not preferred way.

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						Example:

double[] myList;         // preferred way.

or

double myList[];         //  works but not preferred way.

						Creating Arrays:

arrayRefVar = new dataType[arraySize];

						
dataType[] arrayRefVar = new dataType[arraySize];

						
dataType[] arrayRefVar = {value0, value1, ..., valuek};

						Example:

double[] myList = new double[10];

						Example:

public class TestArray {

   public static void main(String[] args) {
      double[] myList = {1.9, 2.9, 3.4, 3.5};

      // Print all the array elements
      for (int i = 0; i < myList.length; i++) {
         System.out.println(myList[i] + " ");
      }
      // Summing all elements
      double total = 0;
      for (int i = 0; i < myList.length; i++) {
         total += myList[i];
      }
      System.out.println("Total is " + total);
      // Finding the largest element
      double max = myList[0];
      for (int i = 1; i < myList.length; i++) {
         if (myList[i] > max) max = myList[i];
      }
      System.out.println("Max is " + max);
   }
}

						Example:

public class TestArray {

   public static void main(String[] args) {
      double[] myList = {1.9, 2.9, 3.4, 3.5};

      // Print all the array elements
      for (double element: myList) {
         System.out.println(element);
      }
   }
}

						Passing Arrays to Methods:

public static void printArray(int[] array) {
  for (int i = 0; i < array.length; i++) {
    System.out.print(array[i] + " ");
  }
}

						
printArray(new int[]{3, 1, 2, 6, 4, 2});

						Returning an Array from a Method:

public static int[] reverse(int[] list) {
  int[] result = new int[list.length];

  for (int i = 0, j = result.length - 1; i < list.length; i++, j--) {
    result[j] = list[i];
  }
  return result;
}