Top 50 Programming Questions (with Answers) for Performance Testers
#performance#java#groovy#c
Jagadish Rajasekar

Jagadish Rajasekar @jagadish_rajasekar_e86a23

Joined:
Sep 6, 2025

Top 50 Programming Questions (with Answers) for Performance Testers

Publish Date: Sep 6 '25
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Performance testing interviews often include programming questions to validate that you can script, automate, and debug under real-world scenarios.

This guide compiles 50 common questions with answers — covering strings, arrays, algorithms, file handling, JSON/XML, random data, and concurrency — in Java, Groovy (JMeter), and C (LoadRunner).

Use this as a refresher before interviews.

📌 Section 1: Strings (Q1–Q10)

Q1. Reverse a String

Java

String str = "performance";
String rev = new StringBuilder(str).reverse().toString();
System.out.println(rev);
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Groovy

groovy
def str = "performance"
println str.reverse()

C

c
char str[] = "performance";
int i, len = strlen(str);
for(i=len-1; i>=0; i--) printf("%c", str[i]);

Q2. Check Palindrome

java
String str="madam";
System.out.println(str.equals(new StringBuilder(str).reverse().toString()));

groovy
def str="madam"
println str == str.reverse()

c
char str[]="madam"; int i=0, j=strlen(str)-1, flag=1;
while(i<j) if(str[i++]!=str[j--]) flag=0;
printf(flag?"Palindrome":"Not Palindrome");

Q3. Find Substring

java
System.out.println("hello".contains("ell"));

groovy
println "hello".contains("ell")

c
printf(strstr("hello","ell")?"Found":"Not Found");

Q4. Count Vowels

java
String s="performance"; long count=s.chars().filter(c->"aeiou".indexOf(c)!=-1).count();
System.out.println(count);

groovy
println "performance".count{ it in ['a','e','i','o','u'] }

c
char s[]="performance"; int c=0;
for(int i=0;i<strlen(s);i++) if(strchr("aeiou",s[i])) c++;
printf("%d",c);

Q5. Remove Whitespace

java
System.out.println("a b c".replaceAll("\\s",""));

groovy
println "a b c".replaceAll("\\s","")

c
// copy only non-space chars

Q6. Find Duplicate Characters

java
String s="testing";
Map<Character,Integer> map=new HashMap<>();
for(char c:s.toCharArray()) map.put(c,map.getOrDefault(c,0)+1);
map.forEach((k,v)->{if(v>1)System.out.println(k);});

Q7. String Compression

Input: aaabbc → Output: a3b2c1

java
String s="aaabbc"; StringBuilder sb=new StringBuilder();
for(int i=0;i<s.length();) {
int j=i; while(j<s.length() && s.charAt(i)==s.charAt(j)) j++;
sb.append(s.charAt(i)).append(j-i); i=j;
}
System.out.println(sb);

Q8. Anagram Check

java
char[] a="listen".toCharArray(), b="silent".toCharArray();
Arrays.sort(a); Arrays.sort(b);
System.out.println(Arrays.equals(a,b));

Q9. Extract Tokens from URL

java
String url="https://site.com?id=123&user=john";
String[] parts=url.split("\\?");
System.out.println(parts[1]); // id=123&user=john

Q10. Replace Words

java
System.out.println("LoadRunner vs JMeter".replace("vs","and"));

📌 Section 2: Arrays & Collections (Q11–Q20)

Q11. Find Duplicates

java
int[] arr={1,2,3,2,1};
Set<Integer> set=new HashSet<>();
for(int n:arr) if(!set.add(n)) System.out.println("Dup:"+n);

Q12. Find Missing Number (1..N)

java
int[] arr={1,2,4,5}; int n=5, sum=n*(n+1)/2, s=0;
for(int x:arr) s+=x;
System.out.println("Missing:"+(sum-s));

Q13. Max/Min

java
int[] arr={3,5,1};
System.out.println(Arrays.stream(arr).max().getAsInt());

Q14. Reverse an Array

java
int[] arr={1,2,3};
for(int i=0,j=arr.length-1;i<j;i++,j--){
int tmp=arr[i]; arr[i]=arr[j]; arr[j]=tmp;
}

Q15. Rotate Array

java
Collections.rotate(Arrays.asList(arr),2);

Q16. Check Sorted

java
boolean sorted=IntStream.range(1,arr.length).allMatch(i->arr[i]>=arr[i-1]);

Q17. Common Elements

java
Set<Integer> s1=new HashSet<>(Arrays.asList(1,2,3));
Set<Integer> s2=new HashSet<>(Arrays.asList(2,3,4));
s1.retainAll(s2);
System.out.println(s1);

Q18. Merge Two Sorted Arrays

java
// classic merge procedure

Q19. Remove Duplicates

java
Arrays.stream(arr).distinct().toArray();

Q20. Frequency Count

java
Map<Integer,Long> freq=Arrays.stream(arr).boxed()
.collect(Collectors.groupingBy(i->i,Collectors.counting()));

📌 Section 3: Numbers & Algorithms (Q21–Q30)

Q21. Fibonacci

java
int a=0,b=1;
for(int i=0;i<10;i++){System.out.print(a+" "); int c=a+b; a=b;b=c;}

Q22. Factorial

java
int f=1,n=5;
for(int i=1;i<=n;i++) f*=i;

Q23. Prime Check

java
int n=17; boolean prime=IntStream.range(2,n).noneMatch(i->n%i==0);

Q24. Armstrong Number

java
int n=153,sum=0,t=n;
while(t>0){int d=t%10; sum+=d*d*d; t/=10;}
System.out.println(sum==n);

Q25. Sum of Digits

java
int n=1234,sum=0;
while(n>0){sum+=n%10;n/=10;}

Q26. Swap Numbers (No Temp)

java
a=a+b; b=a-b; a=a-b;

Q27. GCD

java
int gcd(int a,int b){return b==0?a:gcd(b,a%b);}

Q28. Binary Search

java
int bs(int arr[],int x){
int l=0,h=arr.length-1;
while(l<=h){int m=(l+h)/2;
if(arr[m]==x)return m;
if(arr[m]<x) l=m+1; else h=m-1;}
return -1;
}

Q29. Bubble Sort

java
for(int i=0;i<n-1;i++)for(int j=0;j<n-i-1;j++)
if(arr[j]>arr[j+1]){int t=arr[j];arr[j]=arr[j+1];arr[j+1]=t;}

Q30. Quick Sort

java
// standard partition-based algorithm

📌 Section 4: Data Structures (Q31–Q35)

Q31. Stack

java
Stack<Integer> st=new Stack<>();
st.push(1); st.pop();

Q32. Queue

java
Queue<Integer> q=new LinkedList<>();
q.add(1); q.remove();

Q33. Reverse Linked List

java
// iterative reversal

Q34. Word Count

java
String s="this is test this";
Map<String,Long> map=Arrays.stream(s.split(" "))
.collect(Collectors.groupingBy(w->w,Collectors.counting()));

Q35. Balanced Parentheses

java
// use stack to check if '(' matches ')'

📌 Section 5: File Handling (Q36–Q40)

Q36. Read File

java
Files.lines(Paths.get("file.txt")).forEach(System.out::println);

Q37. Write File

java
Files.write(Paths.get("out.txt"), "hello".getBytes());

Q38. Count Lines

java
long lines=Files.lines(Paths.get("file.txt")).count();

Q39. Search Keyword

java
Files.lines(Paths.get("file.txt")).filter(l->l.contains("error")).forEach(System.out::println);

Q40. Parse CSV

java
Files.lines(Paths.get("data.csv")).map(l->l.split(",")).forEach(arr->System.out.println(arr[0]));

📌 Section 6: JSON & XML (Q41–Q45)

Q41. Parse JSON

java
import org.json.*;
JSONObject obj=new JSONObject("{\"user\":\"john\",\"token\":\"xyz\"}");
System.out.println(obj.getString("token"));

Q42. Convert Object to JSON

java
JSONObject obj=new JSONObject();
obj.put("id",123); obj.put("name","test");

Q43. Parse XML

java
Document doc=DocumentBuilderFactory.newInstance().newDocumentBuilder().parse("file.xml");

Q44. Count XML Nodes

java
NodeList list=doc.getElementsByTagName("user");
System.out.println(list.getLength());

Q45. Validate JSON Contains Key

java
System.out.println(obj.has("token"));

📌 Section 7: Random Data (Q46–Q48)

Q46. Random Number

java
int n=new Random().nextInt(100);

Q47. UUID

java
String id=UUID.randomUUID().toString();

Q48. Shuffle

java
List<Integer> list=Arrays.asList(1,2,3,4,5);
Collections.shuffle(list);

📌 Section 8: Concurrency (Q49–Q50)

Q49. Threads

java
for(int i=0;i<5;i++){
new Thread(()->System.out.println("Hello "+Thread.currentThread().getId())).start();
}

Q50. Synchronization

java
class Counter{int c=0; synchronized void inc(){c++;}}
Counter ct=new Counter();

✅ Final Takeaway

Performance testers/engineers don’t need to be full-time developers — but being comfortable with strings, arrays, file I/O, JSON/XML parsing, and multithreading basics makes you stand out.
These 50 questions cover the most common interview checks across JMeter, LoadRunner, and real-world scripting.

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