Java for Testers – Interview Questions and Answers Part-13
1) Java Program: Change a string such that first character is upper case, second is lower case and so on?
public static String changeToUpperCase(String str) {
StringBuffer s = new StringBuffer();
char ch = ' ';
for (int i = 0; i < str.length(); i++) {
if (ch == ' ' && str.charAt(i) != ' ')
s.append(Character.toUpperCase(str.charAt(i)));
else
s.append(str.charAt(i));
ch = str.charAt(i);
}
return s.toString().trim();
}
2) Java Program: To find duplicates in a list?
public static Set<String> findDuplicates(List<String> listDuplicates) {
final Set<String> set1 = new HashSet<String>();
final Set<String> set2 = new HashSet<String>();
for (String str : listDuplicates) {
if (!set1.add(str)) {
set2.add(str);
}
}
return set2;
}
3) Write a program to compare two Hashmap for equality?
public static Boolean compareMaps(){
Map<String, String> country1 = new HashMap<String, String>();
country1.put("Japan", "Tokyo");
country1.put("China", "Beijing");
Map<String, String> country2 = new HashMap<String, String>();
country2.put("Japan", "Tokyo");
country2.put("China", "Beijing");
if(country1==country2){
return true;
} else
return false;
}
4) Write a Java program to demonstrate creating an Array?
public static void main (String[] args)
{
int[] arr;
arr = new int[5];
arr[0] = 10;
arr[1] = 20;
arr[2] = 30;
arr[3] = 40;
arr[4] = 50;
for (int i = 0; i < arr.length; i++)
System.out.println("Element at index " + i + " : "+ arr[i]);
}
5) Java Program: String s = “sub53od73th”; Eliminate the numbers alone. Print the Alphabets.
public static String removeNumFromString(String str) {
if (str == null) {
return null;
}
char[] ch = str.toCharArray();
int length = ch.length;
StringBuilder sb = new StringBuilder();
int i = 0;
while (i < length) {
if (Character.isDigit(ch[i])) {
i++;
} else {
sb.append(ch[i]);
i++;
}
}
return sb.toString();
}
6) Java program: Reverse the words in the sentence?
public static String reverseTheSentence(String inputString)
{
String[] words = inputString.split("\s");
String outputString = "";
for (int i = words.length-1; i >= 0; i--)
{
outputString = outputString + words[i] + " ";
}
return outputString;
}
7) Java program: Find the count of each element in a two dimensional matrix?
static void printCount(int a[][], int n, int m, int z[], int l)
{
for (int i = 0; i < n; i++)
{
Map<Integer,Integer> mp = new HashMap<>();
for (int j = 0; j < m; j++)
mp.put(a[i][j], 1);
int count = 0;
for (int j = 0; j < l; j++)
{
if (mp.containsKey(z[j]))
count += 1;
}
System.out.println("row" +(i + 1) + " = " + count);
}
8) Java Program: Find duplicate elements in an array of numbers?
public static void main(String[] args) {
int [] arr = new int [] {1, 2, 3, 4, 2, 7, 8, 8, 3};
System.out.println("Duplicate elements in given array: ");
for(int i = 0; i < arr.length; i++) {
for(int j = i + 1; j < arr.length; j++) {
if(arr[i] == arr[j])
System.out.println(arr[j]);
}
}
}
9) Write a program to read/write data from a Property file?
public static void main(String[] args){
Properties prop = new Properties();
prop.setProperty("db.url", "localhost");
prop.setProperty("db.user", "mkyong");
prop.setProperty("db.password", "password");
prop.store(outputStream, "");
prop.load(inputStream)
prop.getProperty("db.url");
prop.getProperty("db.user");
prop.getProperty("db.password");
prop.keySet();
prop.forEach((k, v) -> System.out.println("Key : " + k + ", Value : " + v));
}
10) Write a Java program to demonstrate creating factorial of a number using recursion?
static int factorial(int n){
if (n == 0)
return 1;
else
return(n * factorial(n-1));
}
public static void main(String args[]){
int i,fact=1;
int number=4;
fact = factorial(number);
System.out.println("Factorial of "+number+" is: "+fact);
}
}
11) Java Program: To print the frequency of words in a paragraph?
public static void frequencyWords(String strInput){
Map<String, Integer> occurrences = new HashMap<String, Integer>();
String[] words = strInput.split("\\s+");
for(String word: words){
if(occurrences.containsKey(word)){
int count = occurrences.get(word);
map.put(word,count+1);
} else {
map.put(word,1);
}
}for(Map.Entry<String,Integer> entry: map.entrySet()){
System.out.println(entry.getKey() + ":" + entry.getValue());
}
}
12) Write a Java program to see the output as 0,1,1,2,3?
public static void main(String args[])
{
int n1=0,n2=1,n3,count=5;
System.out.print(n1+" "+n2);
for(int i=2;i<count;i++)
{
n3=n1+n2;
System.out.print(" "+n3);
n1=n2;
n2=n3;
} }
13) Write a java program to find the factorial of a given number ?
public static void findFactorial(int number){
int i,fact=1;
for(i=1;i<=number;i++){
fact=fact*i;
}
System.out.println("Factorial of " + number + "is: " + fact);
}
14) Write a Java program to demonstrate ArrayList?
class ArrayListExample {
public static void main(String[] args)
{
int n = 5;
ArrayList<Integer> arrList = new ArrayList<Integer>(n);
for (int i = 1; i <= n; i++)
arrList.add(i);
System.out.println(arrList);
arrList.remove(3);
System.out.println(arrList);
for (int i = 0; i < arrList.size(); i++)
System.out.print(arrList.get(i) + " ");
}
}
15) Write a Java program to demonstrate LinkedList?
public class LinkedListExample {
public static void main(String args[])
{
LinkedList<String> list = new LinkedList<String>();
list.add("A");
list.add("B");
list.addLast("C");
list.addFirst("D");
list.add(2, "E");
System.out.println(list);
list.remove("B");
list.remove(3);
list.removeFirst();
list.removeLast();
System.out.println(list);
}
}
16) Write a Java program to demonstrate ArrayList using List interface?
class ArrayListWithListInterface {
public static void main(String[] args)
{
List<String> arrayList = new ArrayList<String>();
arrayList.add("Java");
arrayList.add("C#");
arrayList.add("Python");
System.out.println(arrayList);
}
}
17) Write a Java program to demonstrate Hashset?
class HashSetExample{
public static void main(String[] args){
Set<String> hs = new HashSet<String>();
hs.add("India");
hs.add("Australia");
hs.add("South Africa");
hs.add("India");
System.out.println(hs);
}
}
18) Write a Java program to demonstrate LinkedHashSet?
public class LinkedHashSetExample
{
public static void main(String[] args)
{
LinkedHashSet<String> linkedset = new LinkedHashSet<String>();
linkedset.add("A");
linkedset.add("B");
linkedset.add("C");
linkedset.add("D");
System.out.println(linkedset);
}
}
19) Write a Java program to demonstrate TreeSet?
class TreeSetExample {
public static void main(String[] args)
{
TreeSet<String> ts1 = new TreeSet<String>();
ts1.add("A");
ts1.add("B");
ts1.add("C");
ts1.add("C");
System.out.println(ts1);
}
}
20) Write a Java program to demonstrate PriorityQueue?
class PriorityQueueExample {
public static void main(String args[])
{
PriorityQueue<Integer> pQueue = new PriorityQueue<Integer>();
pQueue.add(10);
pQueue.add(20);
pQueue.add(15);
System.out.println(pQueue.peek());
System.out.println(pQueue.poll());
}
}
21) Write a Java program to demonstrate creating HashMap using Map interface?
class HashMapExample{
public static void main(String[] args){
Map<Integer,String> h1 = new HashMap<>();
h1.put(1,"Java");
h1.put(2,"C#");
h1.put(3,"Python");
System.out.println(h1);
}
}
22) Write a Java program to demonstrate LinkedHashMap ?
public class LinkedHashMapExample
{
public static void main(String a[])
{
LinkedHashMap<String, String> map = new LinkedHashMap<String, String>();
map.put("one", "www.gmail.com");
map.put("two", "www.ymail.com");
map.put("four", "www.outlook.com");
System.out.println(lhm);
}
}
23) Write a Java program to demonstrate TreeMap?
class TreeMapExample{
public static void main(String args[]){
TreeMap<Integer,String> map=new TreeMap<Integer,String>();
map.put(100,"Amit");
map.put(102,"Ravi");
map.put(101,"Vijay");
map.put(103,"Rahul");
for(Map.Entry m:map.entrySet()){
System.out.println(m.getKey()+" "+m.getValue());
}
}
}
24) Write a Java program to demonstrate Hashtable?
class HashtableExample{
public static void main(String args[]){
Hashtable<Integer,String> hm=new Hashtable<Integer,String>();
hm.put(100,"Jeorge");
hm.put(102,"Smith");
hm.put(101,"Sarah");
hm.put(103,"John");
for(Map.Entry m:hm.entrySet()){
System.out.println(m.getKey()+" "+m.getValue());
}
}
}
25) Write a Java program to demonstrate creating Multidimensional array?
class MultiExample {
public static void main(String[] args)
{
int[][] arr = { { 1, 2 }, { 3, 4 } };
for (int i = 0; i < 2; i++)
for (int j = 0; j < 2; j++)
System.out.println("arr[" + i + "][" + j + "] = "
+ arr[i][j]);
}
}
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Very helpful java questions.Thanks a lot.
Welcome Kpg 🙂