Develop Reference

How to find largest sequence of numbers in a line?

I have a class assignment where we have to use Math.random to generate values of 0 or 1 representing heads and tails respectively. The point of the program is to have the user input the number of times the coin is flipped, and the program then spits out a string of random 0s and 1s representing the flips. The program then has to find and state the longest number of heads in a row.
eg.
(heads = 0 / tails = 1)
number of tosses: 10
result: 0001100100
longest sequence of heads: 3
this is what I have so far:
import java.util.Scanner;
import java.lang.Math;
public class CoinFlip
{
public static void main(String args[])
{
int Toss; // State variable for tosses
int Heads; // State variable for # of heads
System.out.println("Enter number of tosses:");
Scanner input1 = new Scanner(System.in);
Toss = input1.nextInt();
for(int i = 0; i < Toss ; i++)
{
int Coin = (int) (Math.random() + .5);
System.out.print(Coin); // Prints sequence of flips
}
System.out.println("");
System.out.println("Longest sequence of heads is "); // Says largest sequence of heads
}
}
I'm stuck as to how I read the sequence and then display the longest consecutive head count.

I have written a function to do this. I take the String that you were printing and made a String out of it. I pass this string as a parameter to the function and count the consecutive 0 in it.
This is the code for the same:
import java.util.Scanner;
public class CoinFlip {
public static void main(String args[]) {
int Toss; // State variable for tosses
System.out.println("Enter number of tosses:");
Scanner input1 = new Scanner(System.in);
Toss = input1.nextInt();
StringBuffer coinSequenceBuffer = new StringBuffer(Toss);
for (int i = 0; i < Toss; i++) {
int Coin = (int) (Math.random() + .5);
System.out.print(Coin); // Prints sequence of flips
coinSequenceBuffer.append(Coin);
}
String coinSequence = coinSequenceBuffer.toString();
System.out.println("");
int numberOfConsecutiveHead = findNumberOfConsecutiveHead(coinSequence);
System.out.println("Longest sequence of heads is " + numberOfConsecutiveHead);
}
private static int findNumberOfConsecutiveHead(String coinSequence) {
int count = 1;
int max = 0;
// Starting loop from 1 since we want to compare it with the char at index 0
for (int i = 1; i < coinSequence.length(); i++) {
if (coinSequence.charAt(i) == '1') {
// Since we are not intersted in counting 1's as per the question
continue;
}
if (coinSequence.charAt(i) == coinSequence.charAt(i - 1)) {
count++;
} else {
if (count > max) { // Record current run length, is it the maximum?
max = count;
}
count = 1; // Reset the count
}
}
if (count > max) {
max = count;
}
return max;
}
}
I have tried adding comments so that you can easily understand it. Let me know if you face any issue in understanding it.

This is pretty simple. Just count zeros and reset counter when not zero.
public static void main(String... args) {
System.out.print("Enter number of tosses: ");
int[] arr = new int[new Scanner(System.in).nextInt()];
Random random = new Random();
for (int i = 0; i < arr.length; i++)
arr[i] = random.nextInt(2);
System.out.println(Arrays.toString(arr));
System.out.println("Longest sequence of heads is " + findLongestZeroSequence(arr));
}
public static int findLongestZeroSequence(int... arr) {
int res = 0;
for (int i = 0, cur = 0; i < arr.length; i++) {
if (arr[i] == 0)
res = Math.max(res, ++cur);
else
cur = 0;
}
return res;
}

Here's my go at it:
class CoinFlip {
public static void main(String args[])
{
// Get number of tosses from user
System.out.print("Enter number of tosses: ");
System.out.flush();
Scanner input1 = new Scanner(System.in);
int toss = input1.nextInt();
// Build a string of random '0's and '1's of the specified length (number of tosses)
StringBuilder sb = new StringBuilder();
for(int i = 0; i < toss ; i++)
{
long coin = Math.round(Math.random());
sb.append(coin == 0? '0' : '1');
}
String seq = sb.toString();
// Print the generated String
System.out.println(seq);
// Walk through the string tallying up runs of heads
int count = 0;
int max = 0;
for (int i = 0 ; i < seq.length() ; i++) {
if (seq.charAt(i) == '0') {
count += 1;
} else {
if (count > max)
max = count;
count = 0;
}
}
// Gotta check at the end to see if the longest sequence of heads
// was at the end of the string
if (count > max)
max = count;
// Print the length of the longest sequence
System.out.println("Longest sequence of heads is " + max);
}
}
Sample run:
Enter number of tosses: 40
1000001000000010010101011000011100001000
Longest sequence of heads is 7

Explanations after the code.
import java.util.Scanner;
public class CoinFlip {
private static final int HEADS = 0;
private static final int TAILS = 1;
public static void main(String[] args) {
Scanner input1 = new Scanner(System.in);
System.out.print("Enter number of tosses: ");
int toss = input1.nextInt();
int count = 0;
int longest = 0;
StringBuilder sb = new StringBuilder(toss);
for (int i = 0; i < toss; i++) {
int coin = (int) ((Math.random() * 10) % 2);
sb.append(coin);
System.out.printf("Got %d [%s]%n", coin, (coin == HEADS ? "HEADS" : "TAILS"));
if (coin == HEADS) {
count++;
System.out.println("count = " + count);
}
else {
if (count > longest) {
longest = count;
System.out.println("longest = " + longest);
}
count = 0;
}
}
if (count > longest) {
longest = count;
System.out.println("longest = " + longest);
}
System.out.println(sb);
System.out.print("Longest sequence of heads is " + longest);
}
}
In order to generate a random number which must be either 0 (zero) or 1 (one), I call method random() of class java.lang.Math. The method returns a double between 0.0 and 1.0. Multiplying by ten and then performing modulo 2 operation on that number returns either 0.0 or 1.0 which is a double and therefore needs to be cast to an int.
Each time the above calculation returns 0 (zero) I increment a count. If the calculation returns 1 (one) then I check whether the count is greater than longest and update longest accordingly, after which I reset the count back to zero.
Note that if the last toss is "heads" then the check for the longest sequence will not be performed. Hence I repeat the check for the longest sequence after the for loop.
At the end of the for loop, I have all the required information, i.e. the string that records all the results of all the coin tosses plus the longest sequence of heads.
Here is sample output:
Enter number of tosses: 10
Got 1 [TAILS]
Got 1 [TAILS]
Got 1 [TAILS]
Got 0 [HEADS]
count = 1
Got 1 [TAILS]
longest = 1
Got 0 [HEADS]
count = 1
Got 0 [HEADS]
count = 2
Got 1 [TAILS]
longest = 2
Got 0 [HEADS]
count = 1
Got 0 [HEADS]
count = 2
1110100100
Longest sequence of heads is 2

Printing Prime Numbers to N value

This program is supposed to print all the prime numbers up to an int that you enter, for example:
Enter a Number:
20
2
3
5
7
11
13
17
19
I just cannot get my program to work, I really don't know what to do, so if someone could review it and try to fix it, that would be greatly appreciated, thanks.
import java.util.Scanner;
public class PrimeGenerator {
public static void main(String args[]) {
Scanner k = new Scanner(System.in);
System.out.println("Enter an integer");
int number = k.nextInt();
PrimeGenerator matt = new PrimeGenerator();
System.out.println(matt.nextPrime(number));
}
private int number;
public PrimeGenerator(int n) {
number = n;
}
public int nextPrime(int number) {
for (int i = 1; i <= number; i++) {
boolean prime = true;
for (int j = 2; j < i; j++) {
if (i % j == 0) {
prime = false;
}
}
if (prime){
return i;
}
}
}
}

You're already there actually. You've just got a mistake in the program-flow.
for (int i = 1; i <= number; i++) {
boolean prime = true;
for (int j = 2; j < i; j++) {
if (i % j == 0) {
prime = false;
}
}
if (prime){
return i; //<-- this return will terminate nextPrim
}
}
Things to fix/improve:
nextPrim would need to return a value within every possible program-branch. This means: consider the case where nextPrim doesn't find any number in the given range and steps out of the loop. Now the program would be stuck without any return-value.
Instead of returning the first prim-number found, you could print that found prim-number and keep the generator running. Nice, easy and solves the hassle with returning anything, since you now can simply declare nextPrim as void. I'd recommend renaming it to printPrims or something like that to make this change clear.
Passing number: You can save a bit of effort by only passing number once to the prim-generator. The simplest solution would be to pass it to nextPrim/printPrims. Now you can remove the instance-variable number and the constructor, which solves the issue with th e signature of the constructor.
1 is not a prim-number to be pedantic. So let's be pedantic and start the outer loop in printPrims with 2, so that 2 will be the first number that is checked for being a prim.
So let's put this into code:
import java.util.Scanner;
public class PrimeGenerator {
public static void main(String args[]) {
Scanner k = new Scanner(System.in);
System.out.println("Enter an integer");
int number = k.nextInt();
PrimeGenerator matt = new PrimeGenerator();
matt.printPrims(number);
}
public void printPrime(int number) {
for (int i = 2; i <= number; i++) {
boolean prime = true;
for (int j = 2; j < i; j++) {
if (i % j == 0) {
prime = false;
}
}
if (prime){
System.out.println(i);
}
}
}
A few general hints:
Work through compiler errors. They tell you precisely where and what errors occur within your code.
Think about the flow of your program before even implementing it.
Break the task down into smaller tasks and implement these one after another. As an example: for this problem first print out all numbers in the range 2, number. Afterwards go a step further and add functionality to filter out prim-numbers. Now you've got two components that you can easily test independent of each other.

You were nearly there but your nextPrimes function was terminating prematurely when you returned i, try something like this:
import java.util.Scanner;
class Main {
public static void main(String[] args) {
Scanner k = new Scanner(System.in);
System.out.print("Enter an integer:");
int number = k.nextInt();
printPrimesUptoN(number);
}
public static void printPrimesUptoN(int n){
for(int i=2;i<n;i++){
boolean isPrime = true;
for(int j=2;j<i;j++){
if(i % j == 0){
isPrime = false;
break;
}
}
if(isPrime)
System.out.println(i);
}
}
}
Try it here!

There's a few issues with your code, maybe we can fix it together. First things first, you're missing a return statement in nextPrime and there's no empty default constructor PrimeGenerator() because you created a single-arg constructor. Try this:
public class PrimeGenerator {
public static void main(String args[]) {
Scanner k = new Scanner(System.in);
System.out.println("Enter an integer");
int number = k.nextInt();
// you probably want to pass your maximum value to the constructor
PrimeGenerator matt = new PrimeGenerator(number);
// without a loop of some sort this will only print a single prime number, e.g.
// Enter a Number:
// 20
// 2
System.out.println(matt.nextPrime(number));
}
private int number;
public PrimeGenerator(int n) {
this.number = n;
}
// you're using the argument as upper boundary for your prime detection while not increasing your lower boundary
// also you're checking if i is a prime here which you always start at 1. this should always return the same value because once you find a prime number you return
// you should consider using an algorithm like Sieve of Eratosthenes (or advanced verions thereof) to determine if a given number is prime
public int nextPrime(int number) {
for (int i = 1; i <= number; i++) {
boolean prime = true;
for (int j = 2; j < i; j++) {
if (i % j == 0) {
prime = false;
}
}
if (prime){
return i;
}
}
// you need to return something at the end of this method or throw an exception
throw new IllegalStateException("no more prime numbers available!");
}
}
This is not a solution which will yield the results you're expecting but it will compile at least. From that point you can move forward and fix the algorithmic issues.

Your original error was in.
PrimeGenerator matt = new PrimeGenerator();
Error:
PrimeGenerator.java:7: error: constructor PrimeGenerator in class PrimeGenerator cannot be applied to given types;
PrimeGenerator matt = new PrimeGenerator();
^
required: int
found: no arguments
reason: actual and formal argument lists differ in length
1 error
Notice that you had a method with the same name as you class, but I don't think you were using it as a constructor and if you were it took an int which you didn't give it. Your method on line 13 was:
public PrimeGenerator(int n) {
number = n;
}
Try doing
new PrimeGenerator().nextPrime(number);
Instead
import java.util.Scanner;
public class PrimeGenerator {
public static void main(String args[]) {
Scanner k = new Scanner(System.in);
System.out.println("Enter an integer");
int number = k.nextInt();
new PrimeGenerator().nextPrime(number);
}
public void nextPrime(int number) {
for (int i = 1; i <= number; i++) {
boolean prime = true;
for (int j = 2; j < i; j++) {
if (i % j == 0) {
prime = false;
}
}
if (prime){
System.out.println(i);
}
}
}
}
Optionally, to use your original constructor, you could separate this out.
import java.util.Scanner;
public class PrimeGenerator {
private int number;
public static void main(String args[]) {
Scanner k = new Scanner(System.in);
System.out.println("Enter an integer");
int number = k.nextInt();
// Initialize with a number.
PrimeGenerator pg = new PrimeGenerator(number);
pg.printPrimes();
}
// This is the constructer you were misusing.
public PrimeGenerator(int n) {
number = n;
}
public void printPrimes() {
// Actually use your private number variable.
for (int i = 1; i <= number; i++) {
boolean prime = true;
for (int j = 2; j < i; j++) {
if (i % j == 0) {
prime = false;
}
}
if (prime){
System.out.println(i);
}
}
}
}

There are several issues:
Are you using an IDE? If so, which is it, else Why not?. If you consider yourself a beginner, be advised to used one, like Eclipse IDE or NetBeans IDE.
Regarding to your algorithm, at first glance, there is a compilation and a logic problems.
Compilation problem is when the execution of your class not work. In this case the method nextPrime(int number) MUST return an int. Although you put return clause, the method is not returning any value when prime is false. You could easily spot this problem with an IDE.
Another compilation problem, the sentinel or variable i is INSIDE the for loop, and you are printing it's value OUTSIDE of it. Once again, the IDE would help you with this problem.
Logic problem is, you are returning a value if and only if the flag prime is true, so, when calling the method (supposing is working) you only obtain ONE value when you call System.out.println(matt.nextPrime(number));
The correct implementation would have these considerations:
The method doesn't return, i.e public void nextPrime(number) { ..., which means you don't need print in the main method, just call it.
The method actually prints the numbers.
In this way, you can check if i % j is different of zero, then you don't need to process more dividers, breaking the for loop.
Print it.
That's it.
public static void main(String [] args) {
.
.
.
PrimeGenerator matt = new PrimeGenerator();
matt.nextPrime(number);
}
public void printPrime(int number) {
boolean prime = true;
for (int i = 2; i <= number; i++) {
prime = true;
for (int j = 2; j < i; j++) {
if (i % j != 0) {
prime = false;
break;
}
}
if (prime) {
System.out.println(i);
}
}
}

Java number sequence loop

So hi i'm getting infinite loop problem i don't know whats wrong with my code i'm trying to make a number sequence format is at the bottom i think the problems are in my condition?
import java.util.Scanner;
public class tester {
public static void main(String[] args) {
Scanner x = new Scanner(System.in);
int n;
System.out.print("Enter how many numbers to display");
n = x.nextInt();
while(n!=0) { //is this right?
for ( int i = 0; i<=n; i++) {
if(i%2==0) {
n += 2;
System.out.print(n);
} else {
n += 3;
System.out.print(n);
}
}
}
}
}
Outputs i'm trying to get
Enter how many numbers to display : 5
1 3 6 8 11
2.
Enter how many numbers to display : 16
1 3 6 8 11 13 16 18 21 23 26 28 31 33 36 38 //but im getting infinite loops
// the sequence pattern is +2 then +3

The problem is here: while(n!=0) and here: for ( int i = 0; i<=n; i++). For the while loop, will keep on going until n is equal to 0. For the for loop, this will most likely keep on going for ever.
Your code has two problems:
If you provide a non negative value, this will keep on going for ever (since you are always only incrementing n).
Even if you do supply a negative number, n would n need to become exactly 0 to stop.
Depending on what you need to do, you will need to change the condition. Judging by the output, n would need to be positive and thus you would need to stipulate some upper range for n in which the while loop would stop.
EDIT: You only need to have 1 loop to do what you are after. Also, n denotes the amount of elements, thus it needs to stay fixed throughout the execution of the program. In your case, you where increasing it all the time.
Scanner x = new Scanner(System.in);
int n;
System.out.print("Enter how many numbers to display");
n = x.nextInt();
int count = 0;
int i = 1;
while (count < n) { //is this right?
if (count % 2 == 0) {
System.out.print(i + " ");
i += 2;
} else {
System.out.print(i + " ");
i += 3;
}
count++;
}

Two problems:
int stop = n; // declare one local var to stop the for loop
if (n != 0) { //switch to if condition
for (int i = 0; i <= stop; i++) {
//loop's exit condition wasn't met because 'n' was also being incremented
if (i % 2 == 0) {
n += 2;
System.out.print(n+" ");
} else {
n += 3;
System.out.print(n+" ");
}
}
}

Use 'if' condition in place of 'while' loop

You have to replace your while-loop with an if-condition like so:
import java.util.Scanner;
public class tester {
public static void main(String[] args) {
Scanner x = new Scanner(System.in);
int n;
System.out.print("Enter how many numbers to display");
n = x.nextInt();
int stop = n;
if(n!=0) { //if statement checks if n!=0
for ( int i = 0; i<=stop; i++) {
//stop replaces n because n is incremented in your for-loop
if(i%2==0) {
n += 2;
System.out.print(n);
} else {
n += 3;
System.out.print(n);
}
}
}
}
}

Based on your answers I found a solution that works:
int n;
System.out.print("Enter how many numbers to display");
n = x.nextInt();
int k = -2; // so that it starts with 1 when i add +3
int stop = n-1;
if(n!=0) {
for ( int i = 0; i<=stop; i++) {
if(i%2==0) {
k += 3;
System.out.print(k+" ");
} else {
k += 2;
System.out.print(k+" ");
}
}
}

Ascending order and Descending Java

Hi here's my problem i cant seem to print my outputs correctly i guess i'm having a logical error in my code, it doesn't print when i put an ascending number then a descending. i'm kind of new to programming too.
Code:
import java.util.Scanner;
public class tester {
public static void main(String[] args) {
int n, i, k, j;
int asc = 0,
Scanner x = new Scanner(System.in);
do {
System.out.print("How many numbers to process : ");
k = x.nextInt();
if(k<=1) {
System.out.println("Enter a number greater than 1");
}
} while(k<=1);
System.out.printf("Please enter %d numbers: ",k);
n = x.nextInt();
for(i=0; i<n-1; i++) {
j = x.nextInt();
if( j < n) {
asc++; // is this right?
} else {
asc--;
}
}
if (asc==k) {
System.out.print("Not Growing Up.");
}
if (asc!=k) {
System.out.print("Growing Up.");
}
}
}
Here are the outputs
Example outputs (what i'm trying to get)
How many numbers to process : 4
Please enter 4 numbers : 1 2 3 4
Growing up.
How many numbers to process : 4
Please enter 4 numbers : 4 3 2 1
Not Growing up.
This is my problem :
How many numbers to process : 4
Please enter 4 numbers : 1 2 1 3
Growing up. // it should be not growing up.

There is no need to iterate through all numbers. You can just check if the previous number is lower (if growing). If not, print and return. Check my example code.
Replace
n = x.nextInt();
for (i=0; i<n-1; i++) {
j = x.nextInt();
if( j < n) {
asc++; // is this right?
} else {
asc--;
}
}
if (asc==k) {
System.out.print("Not Growing Up.");
}
if (asc!=k) {
System.out.print("Growing Up.");
}
With
int prev = x.nextInt();
for (i=0; i<k-1; i++) {
j = x.nextInt();
if (j < prev) { System.out.print("Not Growing Up."); return; }
prev = j;
}
System.out.print("Growing Up.");

String numbers = "1 2 3 4"; // Let's take this input for example
int temp = 0; // This use to compare previous integer
boolean isAsc = false; // This store whether the digits is growing up or not
StringTokenizer st = new StringTokenizer(numbers); // Declare StringTokenizer
while (st.hasMoreTokens()) {
int next = Integer.parseInt(st.nextToken()); // Put the first integer in next (1)
if(next > temp){ // if (1) > 0
temp = next; // Assign 1 to temp, next time digit 2 will compare with digit 1
isAsc = true; // Assign the ascending to true
} else
isAsc = false;
}
if(isAsc)
System.out.print("Growing up.");
else
System.out.print("Not growing up.");
}
Your can store the user input as a string like the variable numbers I've declared and break them into each token for compare purpose.

import java.lang.reflect.Array;
import java.util.*;
public class A1 {
public static void main(String[] args) {
int a[]={2,5,0,1};
Arrays.sort(a);
int b= a.length;
for(int i=0;i<a.length;i++)
{
System.out.println(+a[i]+"\t"+a[b-1]);
b--;
}
}
}

Printf Issue or Program Issue?

Trying to take an arraylist of numbers and print out the following...
MOST POPULAR NUMBERS
The following numbers were picked 263 times: 41
LEAST POPULAR NUMBERS
The following numbers were picked 198 times: 20
AVERAGE
The Average was 228.545455 times.
The following numbers were picked 228 times: 5 22
The following numbers were picked 229 times: 2 7 12 40
My code...
import java.util.*;
import java.io.*;
import java.util.Arrays;
import java.util.Collections;
public class Hmwk {
public static void main(String[] args) throws FileNotFoundException {
Scanner input=new Scanner (new File ("input.txt"));
int counter = 0;
ArrayList<Integer> numberList = new ArrayList<Integer>(45);
while(input.hasNextInt()){
int in = input.nextInt();
numberList.add(in);
counter++;
}
mostPopular(numberList,counter);
leastPopular(numberList,counter);
average(numberList,counter);
}
public static void mostPopular(ArrayList<Integer> list, int total){
Collections.sort(list);
int popular = 0;
int counter = 0;
int counterTwo = 0;
for (int i=0; i<total-1; i++){
while(list.get(i) == list.get(i+1)){
counter++;
i++;
if(i == total-1) break;
}
if(counter > counterTwo){
counterTwo = counter;
popular = i;
}
}
System.out.printf("MOST POPULAR NUMBERS");
System.out.printf("The following number was picked",counterTwo,"times:", popular);
}
public static void leastPopular(ArrayList<Integer> list, int total){
Collections.sort(list);
int unpopular=0;
int counter = 0;
int counterTwo = 0;
for (int i=0; i<total-1; i++){
while(list.get(i) == list.get(i+1)){
counter++;
i++;
if(i == total-1) break;
if(counter < counterTwo){
counterTwo = counter;
unpopular = i;
}
}
}
System.out.printf("LEAST POPULAR NUMBERS");
System.out.printf("The following number was picked",counterTwo,"times:", unpopular);
}
public static void average(ArrayList<Integer> list, int total){
int sum = 0;
int counter = 0;
ArrayList<Integer> average = new ArrayList<Integer>(45);
for (int i=0; i<total-1; i++){
while(list.get(i) == list.get(i+1)){
counter++;
i++;
if(i == total-1) break;
}
average.add(counter);
}
for (int i = 0; i <average.size(); i++){
sum+= average.get(i);
}
double average2 = sum/total;
System.out.printf("AVERAGE");
System.out.printf("The Average was",average,"times.");
double ceiling = Math.ceil(average2) ;
double floor = Math.floor(average2);
int counter2 = 0;
Collections.sort(list);
for (int i=0; i<total-1; i++){
while(list.get(i) == list.get(i+1)){
counter2++;
i++;
if(i == total-1) break;
}
if(counter2 == ceiling){
System.out.printf("The following number was picked", ceiling,"times:",i);
}
if (counter2 == floor){
System.out.printf("The following number was picked", floor,"times:",i);
}
}
}
My output is currently...
MOST POPULAR NUMBERSThe following number was pickedLEAST POPULAR NUMBERSThe following number was pickedAVERAGEThe Average was
What I can't seem to figure out is where I went wrong in my program, or if I'm making some stupid mistakes while trying to print out the data. Any and all help is much appreciated, thanks for your time.

printf
The manner in which printf is invoked shows you may have some misconceptions about how it works. printF does NOT concatenate each argument passed to the method. It takes a String containing placeholders as the first parameter and then successive arguments to be assigned to each placeholder.
To invoke printf you need to add placeholders in your initial string and supply the arguments for each placeholder as follows:
System.out.printf("The following number was picked %s times %s",counterTwo, popular);
The code is currently only printing the first String argument which does not have any place holders. The extra arguments supplied to the method are then ignored because no placeholders exist for these arguments to be assigned.
Here is a simple example to help
String stringForFormatting = "Argument %s Argument %s";
String argument1 = "1";
String argument2 = "2";
System.out.printf(stringForFormatting, argument1, argument2); //any other args would be ignored
//outputs Argument 1 Argument 2
New Lines
It also appears that you would like the output to appear on different lines. This can be done in two ways.
First you could add \n to the String:
System.out.printf("MOST POPULAR NUMBERS\n");
But since you really don't need to use printF if the String does not contain any dynamic content (meaning it does not need placeholders), you could use plain System.out.println(), which will add the newline for you:
System.out.println("MOST POPULAR NUMBERS");