1. Write a Java program to reverse an array of integer values.
package com.w3resource;
import java.util.Arrays;
public class ReverseArray {
public static void main(String[] args) {
int[] my_array = {5, 2, 7, 9, 6};
System.out.println("Original array: " + Arrays.toString(my_array));
for (int i = 0; i < my_array.length / 2; i++) {
int temp = my_array[i];
my_array[i] = my_array[my_array.length - i - 1];
my_array[my_array.length - i - 1] = temp;
}
System.out.println("Reverse array: " + Arrays.toString(my_array));
}
}
2. Write a Java program to find the duplicate values of an array of integer values.
package com.w3resource;
public class FindDuplicateElement {
public static void main(String[] args) {
int[] my_array = {5, 2, 7, 7, 5};
for (int i = 0; i < my_array.length - 1; i++) {
for (int j = i + 1; j < my_array.length; j++) {
if ((my_array[i] == my_array[j]) && (i != j)) {
System.out.println("Duplicate Element: " + my_array[j]);
}
}
}
}
}
3. Write a Java program to find the duplicate values of an array of string values.
package com.w3resource;
public class FindDuplicateString {
public static void main(String[] args) {
String[] my_array = {"bcd", "abd", "jude", "bcd", "oiu"};
for (int i = 0; i < my_array.length - 1; i++) {
for (int j = i + 1; j < my_array.length; j++) {
if ( (my_array[i].equals(my_array[j])) && (i != j) ) {
System.out.println("Duplicate Element is: " + my_array[j]);
}
}
}
}
}
4. Write a Java program to find the common elements between two arrays (string values).
package com.w3resource;
import java.util.Arrays;
import java.util.HashSet;
public class FindCommonElement {
public static void main(String[] args) {
String[] my_array = {"Python", "JAVA", "PHP", "C#", "C++", "SQL"};
String[] new_array = {"MySQL", "SQL", "SQLite", "Oracle", "PostgreSQL", "DB2", "JAVA"};
System.out.println("my_array: " + Arrays.toString(my_array));
System.out.println("new_array: " + Arrays.toString(new_array));
HashSet<String> set = new HashSet<String>();
for (int i = 0; i < my_array.length; i++) {
for (int j = 0; j < new_array.length; j++) {
if (my_array[i].equals(new_array[j])) {
set.add(my_array[i]);
}
}
}
System.out.println("Common Element is: " + set);
}
}
Output
Array1 : [Python, JAVA, PHP, C#, C++, SQL]
Array2 : [MySQL, SQL, SQLite, Oracle, PostgreSQL, DB2, JAVA]
Common Element is : [JAVA, SQL]
5. Write a Java program to find the common elements between two arrays of integers.
package com.w3resource;
import java.util.Arrays;
public class CommonIntegerElement {
public static void main(String[] args) {
int[] my_array = {1, 2, 5};
int[] new_array = {6, 5, 8};
System.out.println("my_array: " + Arrays.toString(my_array));
System.out.println("new_array: " + Arrays.toString(new_array));
for (int i = 0; i < my_array.length; i++) {
for (int j = 0; j < new_array.length; j++) {
if (my_array[i] == new_array[j]) {
System.out.println("Common Element is : " + array[i])
}
}
}
}
}
6. Write a Java program to remove duplicate elements from an array.
package com.zetcode;
import java.util.Arrays;
public class RemoveDuplicateElements {
static void unique_array(int[] my_array) {
System.out.println("Original Array : ");
for (int i = 0; i < my_array.length; i++) {
System.out.print(my_array[i] + " ");
}
//Assuming all elements in input array are unique
int no_unique_elements = my_array.length;
//Comparing each element with all other elements
for (int i = 0; i < no_unique_elements; i++) {
for (int j = i + 1; j < no_unique_elements; j++) {
//If any two elements are found equal
if (my_array[i] == my_array[j]) {
//Replace duplicate element with last unique element
my_array[j] = my_array[no_unique_elements - 1];
no_unique_elements--;
j--;
}
}
}
// Copying only unique elements of my_array into array1
int[] new_array = Arrays.copyOf(my_array, no_unique_elements);
// Printing array Without Duplicates
System.out.println();
System.out.println("Array with unique values : ");
for (int i = 0; i < new_array.length; i++) {
System.out.print(new_array[i] + " ");
}
System.out.println();
System.out.println("---------------------------");
}
public static void main(String[] args) {
unique_array(new int[]{0, 3, -2, 4, 3, 2});
unique_array(new int[]{10, 22, 10, 20, 11, 22});
}
}
Output
Original Array :
0 3 -2 4 3 2
Array with unique values :
0 3 -2 4 2
---------------------------
Original Array :
10 22 10 20 11 22
Array with unique values :
10 22 11 20
---------------------------
7. Write a Java program to find the second largest element in an array.
package com.zetcode;
import java.util.Arrays;
public class FindSecondLargest {
public static void main(String[] args) {
int[] my_array = {10789, 2035, 1899, 2046, 2049, 1456, 2013};
System.out.println("Original numeric array: " + Arrays.toString(my_array));
Arrays.sort(my_array);
int index = my_array.length - 1;
while (my_array[index] == my_array[my_array.length - 1]) {
index--;
}
System.out.println("Second largest value: " + my_array[index]);
}
}
8. Write a Java program to find the second smallest element in an array.
package com.zetcode;
import java.util.Arrays;
public class FindSecondSmallest {
public static void main(String[] args) {
int[] my_array = {-1, 4, 0, 2, 7, -3};
System.out.println("Original numeric array : " + Arrays.toString(my_array));
int min = Integer.MAX_VALUE;
int second_min = Integer.MAX_VALUE;
for (int i = 0; i < my_array.length; i++) {
if (my_array[i] == min) {
second_min = min;
} else if (my_array[i] < min) {
second_min = min;
min = my_array[i];
} else if (my_array[i] < second_min) {
second_min = my_array[i];
}
}
System.out.println("Second lowest number is : " + second_min);
}
}