Which For loop will execute first, and finish first?

Im confused over the nested loop variant. Somehow these loops give the same result, but I cant wrap my head around it. like, in the second code, it says in the part of col < values[rows], wouldnt the values[rows] = 4(since there are 4 rows)? So im just wondering how does these loops interact and which one executes first and finishes first?

 for (int row = 0; row < 4; row++)                                    
 {
    for (int col = 0; col < 3; col++)
    {
       System.out.print(values[row][col] + " ");
    }

    System.out.println();   
}

for (int row = 0; row < values.length; row++)
{
   for (int col = 0; col < values[row].length; col++)
   {
      System.out.print(values[row][col] + " ");
   }

   System.out.println();    
}

I am not sure what are you trying to ask here but I guess you just wish to know the difference between the two block of codes.

I'll explain that to you with an simple example:

import java.util.*;
public class HelloWorld{
public static void main(String []args){
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int m = sc.nextInt();
int[][]values = new int[n][m];
for(int i=0; i<n;i++){
for(int j=0; j<m; j++){                //read a 5 x 8 array
values[i][j]= sc.nextInt();
}
}
System.out.print("Input Array :");
for(int i=0; i<n;i++){
for(int j=0; j<m; j++){
System.out.print(values[i][j] +" ");
}
System.out.println("");
}
System.out.print("First Code :");
for (int row = 0; row < 4; row++)                                    
{
for (int col = 0; col < 3; col++)
{
System.out.print(values[row][col] + " ");
}
System.out.println();   
}
System.out.print("Second Code :");    
for (int row = 0; row < values.length; row++)
{
for (int col = 0; col < values[row].length; col++)
{
System.out.print(values[row][col] + " ");
}
System.out.println();    
}    
}
}

Input:

5 8 
3 3 3 3 3 3 3 3 
4 4 4 4 4 4 4 4
5 5 5 5 5 5 5 5 
6 6 6 6 6 6 6 6 
7 7 7 7 7 7 7 7 

Output of the program is:

Input Array :3 3 3 3 3 3 3 3 
4 4 4 4 4 4 4 4 
5 5 5 5 5 5 5 5 
6 6 6 6 6 6 6 6 
7 7 7 7 7 7 7 7 
First Code :3 3 3 
4 4 4 
5 5 5 
6 6 6 
Second Code :3 3 3 3 3 3 3 3 
4 4 4 4 4 4 4 4 
5 5 5 5 5 5 5 5 
6 6 6 6 6 6 6 6 
7 7 7 7 7 7 7 7 

So, as you can see first block works exactly like second block if values.length =4 and values[row].length = 3 otherwise they will give different results. To traverse an array good practice is to go with array.length instead of hard coding the value of length.

In the firs loop:

System.out.print(values[0][0] + " ");

System.out.print(values[0][1] + " ");

System.out.print(values[0][2] + " ");

System.out.print(values[1][0] + " ");

System.out.print(values[1][1] + " ");

System.out.print(values[1][2] + " ");

.......

and so on.... The intern loop will run 4x, since the value of rows = 4. So the output of the intern loop (the col loop) is 4 * 3 = 12 System.out.print(). Get it? Row * Col is the equation that you are looking for. Use it to calc the second code. To help more please show the values defined in values param.

For the For loops in your first section, you are trying to iterate through a 4 x 3 array. So for each row it iterates through the number of columns specified. It stops at the last column of the last row.

For the for loops in your second section, I think it would be more appropriate when you don't know the values for rows and columns.

The first to finish depends on the length of the row in the second case but is fixed on the first one