Java Arrays mismatch(T[] a, T[] b, Comparator<? super T> cmp) Method

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Description

The Java Arrays mismatch(T[] a, T[] b) method finds and returns the first mismatch between two Object arrays. Objects are compared using the provided comparator. In case of no mismatch, -1 is returned. In case of common prefix, length of the common index is returned. In case one array is a proper prefix of other array, smaller array's length is returned.

Declaration

Following is the declaration for java.util.Arrays.mismatch(T[] a, T[] b, Comparator<? super T> cmp) method

public static int mismatch(T[] a, T[] b)

Parameters

• a − This is the first array to be tested for mismatch.

• b − This is the second array to be tested for mismatch.

• cmp − This is the comparator to compare array elements.

Return Value

This method the index of the first mismatch between the two arrays, otherwise -1.

Exception

• NullPointerException − if either array or the comparator is null.

Java Arrays mismatch(T[] a, int aFromIndex, int aToIndex, T[] b, int bFromIndex, int bToIndex ,Comparator<? super T> cmp) Method

Description

The Java Arrays mismatch(T[] a, int aFromIndex, int aToIndex, T[] b, int bFromIndex, int bToIndex) method finds and returns the first mismatch between two T arrays in the given ranges. Objects are compared using the provided comparator. In case of any array null, a NullPointerException is thrown.

Declaration

Following is the declaration for java.util.Arrays.mismatch(T[] a, int aFromIndex, int aToIndex, T[] b, int bFromIndex, int bToIndex) method

public static int mismatch​(T[] a, int aFromIndex, int aToIndex, T[] b, int bFromIndex, int bToIndex)

Parameters

• a − This is the first array to be tested for mismatch.

• aFromIndex − This is the index of the first element (inclusive) of first array to be tested for mismatch.

• aToIndex − This is the index of the last element (exclusive) of first array to be tested for mismatch.

• b − This is the second array to be tested for mismatch.

• bFromIndex − This is the index of the first element (inclusive) of second array to be tested for mismatch.

• bToIndex − This is the index of the last element (exclusive) of second array tto be tested for mismatch.

• cmp − This is the comparator to compare array elements.

Return Value

This method returns the relative index of the first mismatch between the two arrays over the specified ranges, otherwise -1.

Exception

• IllegalArgumentException − if aFromIndex > aToIndex or if bFromIndex > bToIndex

• ArrayIndexOutOfBoundsException − if aFromIndex < 0 or aToIndex > a.length or if bFromIndex < 0 or bToIndex > b.length

• NullPointerException − if either array or the comparator is null

Checking Arrays of Objects for Mismatch Example

The following example shows the usage of Java Arrays mismatch(T[], T[], Comparator) method. First, we've created two arrays of same Student objects, and checked them using mismatch() method. Result is printed.

package com.tutorialspoint;

import java.util.Arrays;
import java.util.Comparator;

public class ArrayDemo {
   public static void main(String[] args) {

      // initialize first students array
      Student array1[] = { new Student(1, "Julie"), new Student(3, "Adam"), new Student(2, "Robert") };

      // initialize second students array
      Student array2[] = { new Student(1, "Julie"), new Student(3, "Adam"), new Student(2, "Robert") };

      RollNoComparator comparator = new RollNoComparator();
      int result = Arrays.mismatch(array1, array2, comparator);
      
      if(result == -1) {
    	  System.out.println("No mismatch. Arrays are same.");
      } else {
    	  System.out.println("First mismatch is at index: " + result);
      }
   }
}
class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
   
   @Override
   public boolean equals(Object obj) {
      Student s = (Student)obj;
      return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name);
   }

   public int getRollNo() {
      return rollNo;
   }

   public void setRollNo(int rollNo) {
      this.rollNo = rollNo;
   }

   public String getName() {
      return name;
   }

   public void setName(String name) {
      this.name = name;
   }
}

class RollNoComparator implements Comparator<Student>{

   @Override
   public int compare(Student o1, Student o2) {
      return o1.getRollNo()-o2.getRollNo();
   }	
}

Output

Let us compile and run the above program, this will produce the following result −

No mismatch. Arrays are same.

Checking Sub-Arrays of Objects for Mismatch Example

The following example shows the usage of Java Arrays mismatch​(T[],int,int,T[],int,int,Comparator) method. First, we've created two arrays of different Student objects, and checked their sub-arrays using mismatch() method. Result is printed.

package com.tutorialspoint;

import java.util.Arrays;
import java.util.Comparator;

public class ArrayDemo {
   public static void main(String[] args) {

      // initialize first students array
      Student array1[] = { new Student(1, "Julie"), new Student(3, "Adam"), new Student(2, "Robert") };

      // initialize second students array
      Student array2[] = { new Student(1, "Julie"), new Student(4, "Jene"), new Student(2, "Robert") };
     
      RollNoComparator comparator = new RollNoComparator();
      int result = Arrays.mismatch(array1, 0, 2, array2, 0, 2, comparator);
      
      if(result == -1) {
    	  System.out.println("No mismatch. Arrays are same.");
      } else {
    	  System.out.println("First mismatch is at index: " + result);
      }
   }
}
class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
   
   @Override
   public boolean equals(Object obj) {
      Student s = (Student)obj;
      return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name);
   }

   public int getRollNo() {
      return rollNo;
   }

   public void setRollNo(int rollNo) {
      this.rollNo = rollNo;
   }

   public String getName() {
      return name;
   }

   public void setName(String name) {
      this.name = name;
   }
}

class RollNoComparator implements Comparator<Student>{

   @Override
   public int compare(Student o1, Student o2) {
      return o1.getRollNo()-o2.getRollNo();
   }	
}

Output

Let us compile and run the above program, this will produce the following result −

First mismatch is at index: 1

Checking Sub-Arrays of Objects for Mismatch Example

The following example shows the usage of Java Arrays mismatch(T[],int,int,T[],int,int,Comparator) method. First, we've created two arrays of different Student objects, and checked their sub-arrays using mismatch() method. Result is printed.

package com.tutorialspoint;

import java.util.Arrays;
import java.util.Comparator;

public class ArrayDemo {
   public static void main(String[] args) {
      // initialize first students array
      Student array1[] = { new Student(1, "Julie"), new Student(3, "Adam"), new Student(2, "Robert") };

      // initialize second students array
      Student array2[] = { new Student(1, "Julie"), new Student(4, "Jene"), new Student(2, "Robert") };

      RollNoComparator comparator = new RollNoComparator();      
      int result = Arrays.mismatch(array1, 2, 2, array2, 2, 2);
      
      if(result == -1) {
    	  System.out.println("No mismatch. Arrays are same.");
      } else {
    	  System.out.println("First mismatch is at index: " + result);
      }
   }
}
class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
   
   @Override
   public boolean equals(Object obj) {
      Student s = (Student)obj;
      return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name);
   }

   public int getRollNo() {
      return rollNo;
   }

   public void setRollNo(int rollNo) {
      this.rollNo = rollNo;
   }

   public String getName() {
      return name;
   }

   public void setName(String name) {
      this.name = name;
   }
}

class RollNoComparator implements Comparator<Student>{

   @Override
   public int compare(Student o1, Student o2) {
      return o1.getRollNo()-o2.getRollNo();
   }	
}

Output

Let us compile and run the above program, this will produce the following result −

No mismatch. Arrays are same.