What new methods are added to the Arrays class in Java 9?

The Arrays class can contain various methods for manipulating arrays, and also contains static factory methods that allow arrays to be treated as lists. Java 9 adds three important methods to the Arrays class: Arrays.equals(), Arrays.compare() and Arrays.mismatch().

Arrays.equal() - In Java 9, several overloaded methods were added to the Arrays.equals() method. The new method adds fromIndex and toIndex parameters to the two provided arrays. These methods check the equality of two arrays based on their relative index positions.

Syntax

<strong>public static boolean equals(int[] a, int aFromIndex, int aToIndex, int[] b, int bFromIndex, int bToIndex)</strong>

In the above syntax, if the two specified int arrays and the elements in the specified range are equal, the method returns true. The second method is the same for char arrays.

Example

import java.util.Arrays;
public class CompareArrayTest {
   public static void arrayEqualsTest() {
      int[] existRows = {0, 1, 2, 3, 4, 5};
      int[] newRows = {3, 4, 5, 1, 2, 0};
      System.out.println(<strong>Arrays</strong>.<strong>equals</strong>(existRows, newRows));
      System.out.println(<strong>Arrays</strong>.<strong>equals</strong>(existRows, 1, 3, newRows, 3, 5));
      System.out.println(<strong>Arrays</strong>.<strong>equals</strong>(existRows, 3, 5, newRows, 0, 2));
   }
   public static void main(String args[]) {
      CompareArrayTest.arrayEqualsTest();
   }
}

Output

false
true
true

##Arrays.compare() − In Java 9, few parameters have added to the Arrays.compare() method. With fromIndex/toIndex parameters that are used for relative position comparison.

<strong>public static int compare(int[] a, int aFromIndex, int aToIndex, int[] b, int bFromIndex, int bToIndex)</strong>

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lexicographically over the specified ranges.

import java.util.Arrays;
public class LexicographicalArraysTest {
   public static void main(String args[]) {
      LexicographicalArraysTest.compareSliceArraysTest();
   }
   public static void compareSliceArraysTest() {
      int[] tomMarks = {5, 6, 7, 8, 9, 10};
      int[] daisyMarks = {5, 6, 7, 10, 9, 10};
      int[] maryMarks = {5, 6, 7, 8};
      System.out.println(<strong>Arrays.compare</strong>(tomMarks, 0, 3, daisyMarks, 0, 3));
      System.out.println(<strong>Arrays.compare</strong>(tomMarks, 0, 4, maryMarks, 0, maryMarks.length));
      System.out.println(<strong>Arrays.compare</strong>(daisyMarks, 0, 4, maryMarks, 0, maryMarks.length));
   }
}

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<strong>0
0
1</strong>

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Arrays.mismatch() −In Java 9, there are other overloaded methods of the Arrays.mismatch() method that enables us to find and return the index of the first mismatch between two slices of arrays.

<strong>public static int mismatch(int[] a, int aFromIndex, int aToIndex, int[] b, int bFromIndex, int bToIndex)</strong>

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relative index of the first mismatch between two int arrays over the specified range. It returns -1 if no mismatch has found. The index in the range of 0 (inclusive) up to the length (inclusive) of the smaller range.

import java.util.Arrays;
public class MismatchMethodTest {
   public static void main(String[] args) {
      MismatchMethodTest.mismatchArraysTest();
   }
   public static void mismatchArraysTest() {
      int[] a = {1, 2, 3, 4, 5};
      int[] b = {1, 2, 3, 4, 5};
      int[] c = {1, 2, 4, 4, 5, 6};
      System.out.println(<strong>Arrays.mismatch</strong>(a, b));
      System.out.println(<strong>Arrays.mismatch</strong>(a, c));
      System.out.println(<strong>Arrays.mismatch</strong>(a, 0, 2, c, 0, 2));
      System.out.println(<strong>Arrays.mismatc</strong><strong>h</strong>(a, 0, 3, c, 0, 3));
      System.out.println(<strong>Arrays.mismatch</strong>(a, 2, a.length, c, 2, 5));
   }
}

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<strong>-1
2
-1
2
0</strong>

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