Java Program to find missing numbers in an array

• To find missing numbers in an array first we need to make sure that array is sorted.
• After sorting we need to check that array each element with next element then we can find the difference.
• if Array is not sorted :To sort array use Arrays.sort(array);
• If difference is 1 then no need to do any thing because numbers are in order.
• If difference is not equal to 1 then we need to print all those numbers or pick those numbers and place it in one array.
• this would be the logic to find missing numbers in an array
• Here there may be a chance of array not starts with 1 then we need to check first itself whether array starts with 1 or not if not we need to print 1 to starting element of array.
• for example int a[]={4,5,6,8}; then we need to print 1 2 3  7.

Lets see a java example program to find missing numbers in an array.

1. 
   

 

 Lets see a java example program to find missing numbers in an array.

1. package arraysInterviewQuestions;
2. public class PrintMissingNumbers {
3.  
4. private static void findMissingNumber(int[] number){
5.  
6.         // take max length as last number in array
7.     int k[] = new int[number[number.length-1]];
8.         
9.   int m=0;
10.  
11.   if(number[0]!=1){
12.    for (int x = 1; x < number[0]; x++) {
13.        k[m] =  x;
14.        m++;
15.        }
16.   }
17.         
18.  for (int i = 0; i < number.length -1; i++) {
19.     
20.     int j = i+1;
21.     int difference = number[j] - number[i] ;
22.             
23.             
24.    if(difference != 1 ){
25.         
26.   for (int x = 1; x < difference; x++) {
27.  
28.           k[m] = number[i] + x;
29.            m++;
30.     
31. }
32.             
33.  }
34.  }
35.         
36. System.out.println("missing numbers in array ::");
37.         
38. for (int l = 0; l < m ; l++) {
39.     System.out.println( k[l]+" ");
40. }
41. }
44.  public static void main(String[] args) {
45.         
46.    int a[]= {2,4,6,9,10,20};
47.  
48.    //if Array is not sorted :To sort array use Arrays.sort(a); 
49.  
50.   findMissingNumber(a);
51.  
52.    
53. }
54. }

 

• Change the array in main method and practice try to find missing elements in an array that contains 1 to 100 numbers.

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How to find uppercase letters in a string in java

• How can we count upper case letter in String  java ?
• How to find uppercase letters in String  java?
• How to find capital letters in string in java?
• How u discover the capital letter given sentence?
• Yes We can find uppercase or capital letters in a String using isUpperCase() method of Character class in java
• In order to find number of uppercase letters in a string of all capital letters in a string we need to iterate all characters of a string in a loop and check individual characters are uppercase letters or not using Character class provided isUpperCase() method.

Program #1: Java example program to find all capital letters / Uppercase letters in a String 

1. package findUppercaseletters.String;
2. public class FinfUppercaseLetters {
3.  
4.     /**
5.      * 
6.      */
7.  
8.  public static void main(String[] args) {
9.         
10.         
11.   String str= "How to Print Uppercase Letters in Java";
12.  
13.     for (int i = 0; i < str.length(); i++) {
14.     
15.             if(Character.isUpperCase(str.charAt(i))){    
16.             System.out.println(str.charAt(i));
17.             }
18.             
19.  }
20.  
21. }
22.  
23. }

 Output:

1. H
2. P
3. U
4. L
5. J

Sort ArrayList in descending order

Descending order:

1. package com.instanceofjavaforus;
2. import java.util.ArrayList;
3.  import java.util.Collections;
4. import java.util.Comparator;
5.  
6. public class SortArrayListDesc {
7.  
8.      public static void main(String[] args) {
9.  
10.             //create an ArrayList object
11.             ArrayList arrayList = new ArrayList();
12.  
13.             //Add elements to Arraylist
14.             arrayList.add(1);
15.             arrayList.add(2);
16.             arrayList.add(3);
17.            arrayList.add(4);
18.             arrayList.add(5);
19.             arrayList.add(6);
20.  
21.             /*
22.            Use static Comparator reverseOrder() method of Collections 
23.         utility class to get comparator object
24.            */
25.  
26.          Comparator comparator = Collections.reverseOrder();
27.  
28.           System.out.println("Before sorting  : "  + arrayList);
29.         
30.  
31.            /*
32.               use
33.               static void sort(List list, Comparator com) method of Collections class.
34.             */
35.  
36.             Collections.sort(arrayList,comparator);
37.             System.out.println("After sorting  : + arrayList);
39.  
40.        }
41.     }
     

1. OutPut:
2. Before sorting  : [1, 2, 3, 4, 5, 6]
3. After sorting  : [6, 5, 4, 3, 2, 1]

1. package com.instanceofjavaforus;
2. import java.util.ArrayList;
3.  import java.util.Collections;
4. import java.util.Comparator;
5.  
6. public class SortArrayListAsc{
7.  
8.      public static void main(String[] args) {
9.  
10.             //create an ArrayList object
11.             ArrayList arrayList = new ArrayList();
12.  
13.             //Add elements to Arraylist
14.             arrayList.add(10);
15.             arrayList.add(4);
16.             arrayList.add(7);
17.            arrayList.add(2);
18.             arrayList.add(5);
19.             arrayList.add(3);
20.  
21.           
22.  
23.           System.out.println("Before sorting  : "  + arrayList);
24.         
25.  
26.            /*
27.               use
28.               static void sort(List list) method of Collections class.
29.             */
30.  
31.             Collections.sort(arrayList);
32.             System.out.println("After sorting  : + arrayList);
34.  
35.        }
36.     }
     

Ascending order:

1. OutPut:
2. Before sorting  : [10, 4, 7, 2, 5, 3]
3. After sorting  : [2, 3, 4, 5, 7, 10]