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Wrong amount of lines in printTriangle?

I've been doing a MOOC.fi Java course and it comes along quite well, except the Christmas Tree part. It works as intended in the output, but the system won't accept it and I don't know why.
I get this error:
when printTriangle(1) was called, wrong amount of lines was printed expected:<1> but was:<2>
Here's the code:
public class AdvancedAstrology {
public static void printStars(int number) {
for(int i = 0; i < number; i++){
System.out.print("*");
}
System.out.println();
}
public static void printSpaces(int number) {
while(number > 0){
System.out.print(' ');
number--;
}
}
public static void printTriangle(int size) {
int star = 0;
while(size > 0){
printSpaces(size--);
printStars(star++);
}
}
public static void christmasTree(int height) {
int h = height -1;
int stand = height - 2;
int s = 1;
while(height > 0){
printSpaces(h);
printStars(s);
s+=2;
h--;
height--;
}
printSpaces(stand);
printStars(3);
printSpaces(stand);
printStars(3);
}
public static void main(String[] args) {
// The tests are not checking the main, so you can modify it freely.
printTriangle(5);
System.out.println("---");
christmasTree(4);
System.out.println("---");
christmasTree(10);
}
}

You're doing post increment, that's why in star is being passed as 0 in first iteration.
public static void printTriangle(int size) {
int star = 0;
while(size > 0){
printSpaces(size--);
printStars(star++); //Here. change it to ++star
}
}

java program giving blank output

The program works fine for small numbers but as soon as i take a big number like this it doesn't work
here is my code
public class Main {
public static void main(String[] args) {
long no=600851475143L,i;
int result=0;
for(i=(no/2);i>=2;i--){
if(no%i==0){
if(checkPrime(i)){
System.out.println("Longest Prime Factor is: " + i);
break;
}
}
}
}
private static boolean checkPrime(long i){
for(long j=2L;j<=(int)Math.sqrt(i);j++){
if(i%j==0)
return false;
}
return true;
}
}

to assign long variable value we does not require write L at last on value Remove L.

It will take time to display the answer. Just try with small number(1000000 ) almost 10 to 15 min for above code.
Try this
public class Main {
public static void main(String[] args) {
//long no=600851475143L,i;
System.out.println(largestPrimeFactor(600851475143L));
}
public static int largestPrimeFactor(long number) {
int i;
for (i = 2; i <= number; i++) {
if (number % i == 0) {
number /= i;
i--;
}
}
return i;
}
}
[1]https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes

Setting up a global variable to count recursions

public class collatzpow {
public static int collatz(int n) {
StdOut.print( n + " ");
if (n == 1) return 0;
if (n% 2 == 0) return collatz(n/2);
else return collatz(3*n + 1);
}
public static void main(String[] args) {
int n= Integer.parseInt(args[0]);
StdOut.println(collatz(7));
}
}
I want to set up a global variable to count the number of time the program calls the recursion. I know with the number 7 it calls it 17 times.
I've been told it is very easy, but I'm struggling a bit with it.

Just declare a static int variable in the class scope and increment each time the method is called.
public class collatzpow {
public static int count = 0;
public static PrintStream StdOut = System.out;
public static int collatz(int n) {
++count;
StdOut.print(n + " ");
if (n == 1) return 0;
if (n % 2 == 0) return collatz(n / 2);
else return collatz(3 * n + 1);
}
public static void main(String[] args) {
int n = Integer.parseInt(args[0]);
StdOut.println(collatz(7));
System.out.println(count);
}
}

Number pyramind, with recursive method. Java Beginner

I am a new member here, and I am also a beginner in JAVA. The thing that seems the most abstract to me is recursion, and so I have some difficulties finishing a program that should have this output if we write 3 for example:
1
12
123
12
1
Or if we write 5 for example it should print out this:
1
12
123
1234
12345
1234
123
12
1
And I can do this program with for loop, but I have to use recursion, and here is what I have done so far:
public class Aufgabe3 {
private static void printSequenz(int n) {
if(n<1){
return;
}
printMany(n);
printSequenz(n-1);
}
private static void printMany(int n){
for(int i=1;i<=n;i++){
System.out.print(i);
}
System.out.println();
}
public static void main(String[] args) {
printSequenz(5);
}
}
I would be really happy if someone would help me :).

You need to implement two recursive functions:
void printLoToHi(int n)
{
if (n < 1)
return;
printLoToHi(n-1);
printMany(n);
}
void printHiToLo(int n)
{
if (n < 1)
return;
printMany(n);
printHiToLo(n-1);
}
Then, you need to call them sequentially:
printSequenz(int n)
{
printLoToHi(n);
printHiToLo(n-1); // -1 in order to avoid printing the highest twice
}
Or in a more "symmetrical manner":
printSequenz(int n)
{
printLoToHi(n-1); // print lowest to second highest
printMany(n); // print the highest
printHiToLo(n-1); // print second highest to lowest
}

You could do it like this:
private static void printSequenz(int n) {
printSequenz(1,n, true);
}
private static void printSequenz(int current, int total, boolean goingUp) {
if(!goingUp && current<1){
return;
}
printMany(current);
if(current+1>total){
goingUp=false;
}
if(goingUp){
printSequenz(current+1,total,goingUp);
} else {
printSequenz(current-1,total,goingUp);
}
}
private static void printMany(int n) {
for (int i = 1; i <= n; i++) {
System.out.print(i);
}
System.out.println();
}
public static void main(String[] args) {
printSequenz(5);
}

public class Test {
public static void main(String args[]) {
int seq = 6;
for(int i=1; i<=seq; i++) {
System.out.println("");
int low =seq-(seq-i);
printIncreasing(i,low);
}
for(int i=seq-1; i>=1; i--) {
System.out.println("");
int low = seq-i;
printDecreasing(i,low);
}
}
public static void printIncreasing(int high, int low) {
for(int i = 1; i<=high;i++ ) {
System.out.print(i);
}
}
public static void printDecreasing(int high, int low) {
for(int i = 1; i<=high;i++ ) {
System.out.print(i);
}
}
}

Java: check if number belongs to Fibonacci sequence

I'm supposed to write a code which checks if a given number belongs to the Fibonacci sequence. After a few hours of hard work this is what i came up with:
public class TP2 {
/**
* #param args
*/
public static boolean ehFibonacci(int n) {
int fib1 = 0;
int fib2 = 1;
do {
int saveFib1 = fib1;
fib1 = fib2;
fib2 = saveFib1 + fib2;
}
while (fib2 <= n);
if (fib2 == n)
return true;
else
return false;
}
public static void main(String[] args) {
int n = 8;
System.out.println(ehFibonacci(n));
}
}
I must be doing something wrong, because it always returns "false". Any tips on how to fix this?

You continue the loop while fib2 <= n, so when you are out of the loop, fib2 is always > n, and so it returns false.

/**
* #param args
*/
public static boolean ehFibonacci(int n) {
int fib1 = 0;
int fib2 = 1;
do {
int saveFib1 = fib1;
fib1 = fib2;
fib2 = saveFib1 + fib2;
}
while (fib2 < n);
if (fib2 == n)
return true;
else
return false;
}
public static void main(String[] args) {
int n = 5;
System.out.println(ehFibonacci(n));
}

This works. I am not sure about efficiency..but this is a foolproof program,
public class isANumberFibonacci {
public static int fibonacci(int seriesLength) {
if (seriesLength == 1 || seriesLength == 2) {
return 1;
} else {
return fibonacci(seriesLength - 1) + fibonacci(seriesLength - 2);
}
}
public static void main(String args[]) {
int number = 4101;
int i = 1;
while (i > 0) {
int fibnumber = fibonacci(i);
if (fibnumber != number) {
if (fibnumber > number) {
System.out.println("Not fib");
break;
} else {
i++;
}
} else {
System.out.println("The number is fibonacci");
break;
}
}
}
}

you can also use perfect square to check whether your number is Fibonacci or not. you can find the code and some explanation at geeksforgeeks.
you can also see stackexchange for the math behind it.

I'm a beginner but this code runs perfectly fine without any issues. Checked with test cases hopefully it'll solve your query.
public static boolean checkMember(int n) {
int x = 0;
int y = 1;
int sum = 0;
boolean isTrue = true;
for (int i = 1; i <= n; i++) {
x = y;
y = sum;
sum = x + y;
if (sum == n) {
isTrue=true;
break;
} else {
isTrue=false;
}
}
return isTrue;
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
System.out.print(checkMember(n));
}