LAST UPDATE: MARCH 6, 2015
Some of these might be found in other library classes such as Arrays (if you find a more efficient implementation feel free to share it)
Feel free to leave constructive feedback (on the code/comments) / suggest methods.
package org.bjornkrols.utilities.array;
import java.util.Comparator;
import java.util.Random;
import org.bjornkrols.algorithms.sequence_search.BinarySearch;
/**
* A set of utility methods for arrays.
*
* @author Bjorn Krols (Botre)
* @version 0.0
* @since March 6, 2015
*/
public final class ArrayUtilities {
private ArrayUtilities() {
// This class should never be instantiated.
// Do not delete or make accessible.
}
private static final Random RANDOM = new Random();
/**
* @return A string representation of the array with the following format: [0, 1, 2, ..., length - 1].
*/
public static String toString(Object[] array) {
if (array == null) {
return "null";
}
int max = array.length - 1;
if (max == -1) {
return "[]";
}
StringBuilder sb = new StringBuilder();
sb.append('[');
for (int i = 0; ; i++) {
sb.append(array[i]);
if (i == max) {
return sb.append(']').toString();
}
sb.append(", ");
}
}
/**
* Calls java.io.PrintStream.println on every entry of the array.
*/
public static void printlnContents(Object[] array) {
if (array == null) {
System.out.println("null");
return;
}
for (int i = 0; i < array.length; i++) {
System.out.println(array[i]);
}
}
/**
* Prints a String representation of the array and terminates the line.
*/
public static void printlnString(Object[] array) {
System.out.println(toString(array));
}
/**
* @return A new array resulting from the concatenation of a set of arrays.
*/
public static int[] concatenate (int[]... arrays) {
int size = 0;
for (int[] array : arrays) size += array.length;
int[] result = new int[size];
int index = 0;
for (int[] array : arrays) for (int element : array) result[index++] = element;
return result;
}
/**
* @see ArrayUtilities#concatenate(int[]...)
*/
public static Object[] concatenate (Object[]... arrays) {
int size = 0;
for (Object[] array : arrays) size += array.length;
Object[] result = new Object[size];
int index = 0;
for (Object[] array : arrays) for (Object element : array) result[index++] = element;
return result;
}
/**
* Swaps the entries at indexes a & b.
*/
public static void swapEntriesByIndex(boolean[] array, int a, int b) {
boolean temp = array[a];
array[a] = array[b];
array[b] = temp;
}
/**
* @see ArrayUtilities#swapEntriesByIndex(boolean[], int, int)
*/
public static void swapEntriesByIndex(byte[] array, int a, int b) {
byte temp = array[a];
array[a] = array[b];
array[b] = temp;
}
/**
* @see ArrayUtilities#swapEntriesByIndex(boolean[], int, int)
*/
public static void swapEntriesByIndex(short[] array, int a, int b) {
short temp = array[a];
array[a] = array[b];
array[b] = temp;
}
/**
* @see ArrayUtilities#swapEntriesByIndex(boolean[], int, int)
*/
public static void swapEntriesByIndex(char[] array, int a, int b) {
char temp = array[a];
array[a] = array[b];
array[b] = temp;
}
/**
* @see ArrayUtilities#swapEntriesByIndex(boolean[], int, int)
*/
public static void swapEntriesByIndex(int[] array, int a, int b) {
int temp = array[a];
array[a] = array[b];
array[b] = temp;
}
/**
* @see ArrayUtilities#swapEntriesByIndex(boolean[], int, int)
*/
public static void swapEntriesByIndex(long[] array, int a, int b) {
long temp = array[a];
array[a] = array[b];
array[b] = temp;
}
/**
* @see ArrayUtilities#swapEntriesByIndex(boolean[], int, int)
*/
public static void swapEntriesByIndex(float[] array, int a, int b) {
float temp = array[a];
array[a] = array[b];
array[b] = temp;
}
/**
* @see ArrayUtilities#swapEntriesByIndex(boolean[], int, int)
*/
public static void swapEntriesByIndex(double[] array, int a, int b) {
double temp = array[a];
array[a] = array[b];
array[b] = temp;
}
/**
* @see ArrayUtilities#swapEntriesByIndex(boolean[], int, int)
*/
public static void swapEntriesByIndex(Object[] array, int a, int b) {
Object temp = array[a];
array[a] = array[b];
array[b] = temp;
}
/**
* @return Whether the array is sorted.
*/
@SuppressWarnings("rawtypes")
public static boolean isSorted(Comparable[] array) {
return isSorted(array, 0, array.length - 1);
}
/**
* @return Whether the array is sorted between indexes low and high.
*/
@SuppressWarnings({ "rawtypes", "unchecked" })
public static boolean isSorted(Comparable[] array, int low, int high) {
for (int i = low + 1; i <= high; i++) if (array[i].compareTo(array[i - 1]) < 0) return false;
return true;
}
/**
* @see ArrayUtilities#isSorted(Comparable[])
*/
@SuppressWarnings("rawtypes")
public static boolean isSorted(Object[] array, Comparator comparator) {
return isSorted(array, comparator, 0, array.length - 1);
}
/**
* @see ArrayUtilities#isSorted(Comparable[], int, int)
*/
@SuppressWarnings({ "rawtypes", "unchecked" })
public static boolean isSorted(Object[] array, Comparator comparator, int low, int high) {
for (int i = low + 1; i <= high; i++) if (comparator.compare(array[i], array[i - 1]) < 0) return false;
return true;
}
/**
* @return Whether the sorted array contains a specific key value.
*/
public static boolean sortedContains(int[] array, int key) {
return BinarySearch.getIndex(array, key) != -1;
}
/**
* Reverses the array.
*/
public static void reverse(int[] array) {
int length = array.length;
for (int i = 0; i < length / 2; i++) {
array[i] = array[i] ^ array[length - i - 1];
array[length - i - 1] = array[i] ^ array[length - i - 1];
array[i] = array[i] ^ array[length - i - 1];
}
}
/**
* @return A random entry from the array.
*/
public static int getRandomEntry(int[] array) {
return array[RANDOM.nextInt(array.length)];
}
}
