返回不兼容的类型（java）

Question

Original: Okay so I have to make a simple number pyramid but the catch is that it has to use two methods. My problem is that return keeps giving me "Incompatible types" and I have no clue as to why. Okay so I have to make a simple number pyramid but the catch is that it has to use two methods. My problem is that return keeps giving me "Incompatible types" and I have no clue as to why.

public static void main(String[] args) 
{
System.out.println(NumPyramid(1,1));
} 
public static int NumPyramid(int i, int j)
 {
    for (;i <= 7; i++) 
{
  for (; j <= i; j++)
{        
{    
   return System.out.print(j + " ");
    }
} 
}

Edit: okay so now my new code has the problem of not being a pyramid

public static void main(String[] args) 
{
    NumPyramid(1,1);
} 
public static void NumPyramid(int i, int j)
{
    for (;i <= 7; i++) 
    {
      for (; j <= i; j++)
      {      
          System.out.print(j + " ");
        }
      System.out.println();
    } 
}

this prints out

1 2 3 4 5 6 7

removing the Println gives 1 2 3 4 5 6 7

The output should be 1 12 123 etc,

Answer 1

System.out.print is a void method; that is, it returns nothing.

You can't return something from a void method.

Simply remove the return keyword from that line, change the signature of your method from int to void .

Then, change the call in your main method to remove the System.out.println from it.

Answer 2

well, as @makoto points out cleverly, System.out.print being a void method, it returns nothing so:

public static void main(String[] args) {
    System.out.println(NumPyramid(1,1));
} 

should be changed as well. So you shall make:

public static void NumPyramid(int i, int j) {
  for (;i <= 7; i++) {
    for (; j <= i; j++) {       
       System.out.print(j + " ");
    }
  } 
}

a void method, and :

public static void main(String[] args) {
    NumPyramid(1,1);
} 

not getting printed.

Edit

When you got a new question, you shall not edit your question, removing stuff in the question's post to make it into a new one… But instead accept the best answer, and make a new post. Here we are not answering only to you , but we are building a knowledge base. If you have a new question, make it a new post!

That said, for your new question, what your algorithm is off, it should instead be:

public static void NumPyramid(int max) {
    for (int i=1; i<=max; ++i) {
        for (int j=1; j<=i; ++j)
            System.out.println(j + " "); 
        System.out.println();
    }
}

• having a single argument max to specify the number of lines, and the width of the "base" of the pyramid ;
• iterate using i for max carriage return output ;
• iterate using j for i numbers
• start iterations at 1, so we don't output 0 1 2 for max = 3 but 1 2 3

which should output, with max = 3

1
1 2
1 2 3

HTH, again. And please, please, restore your original question.

Answer 3

You want to print this?

1 
1 2 
1 2 3 
1 2 3 4 
1 2 3 4 5 

You need one argument, and it's the method:

public static void NumPyramid(int number)
{
    for (int i = 1; i <= number; ++i)
    {
        for (int x = 1; x <= i; ++x)
        {
            System.out.print(x + " ");
        }

        System.out.println();
    }
}

I think it's self-explanatory

Answer 4

I guess you're not asking about incompatible return types anymore? Well, I can answer the question you have now, I think.

If you want the code to be in a pyramid, you can't do this:

for (;i <= 7; i++) 
{
  for (; j <= i; j++)
  {      
      System.out.print(j + " ");
    }
  System.out.println();
} 

What that code is doing is printing the value of j, then a space, and then printing a new line. A solution is to create a String that you use to store the numbers after each iteration of the for loops.

for (;i <= 7; i++) 
{
  for (; j <= i; j++)
  {      
      //System.out.print(j + " ");
      //The string would take the place of this line
    }
  //Since println always prints on a new line, you 
  //could just print the string in this System.out
  System.out.println();
}