I've been learning Java for a while and I've run into a problem I can't figure out. I am currently learning arrays and how to iterate through them using loops. I generally understand how the if statement and the for loop work, but in this case I don't understand the principle of this loop in combination with if statements. This is the example I'm talking about:

class MinMax {
    public static void main(String[] args) {

        int nums[] = new int[10];
        int min, max;

        nums[0] = 99;
        nums[1] = -10;
        nums[2] = 100123;
        nums[3] = 18;
        nums[4] = -978;
        nums[5] = 5623;
        nums[6] = 463;
        nums[7] = -9;
        nums[8] = 287;
        nums[9] = 49;

        min = max = nums[0];
        for (int i = 1; i < 10 ; i  ){
            if (nums[i] < min) min = nums[i];
            if (nums[i] > max) max = nums[i];
        }
        System.out.println("Largest and smallest value: "   min   " "   max);

    }
}

I want to focus on this part:

        min = max = nums[0];
        for (int i = 1; i < 10 ; i  ){
            if (nums[i] < min) min = nums[i];
            if (nums[i] > max) max = nums[i];

The only thing I understand from this is how this for loop works, but the instruction min = max = nums[0]; is unclear to me. Why are we assigning these values to each other? Probably because I don't understand this instruction I also can't understand the principle of if statements in this example.

Can someone explain it to me step by step please?

CodePudding user response：

min = max = nums[0];

is simply a short way of writing

min = nums[0];
max = nums[0];

because the "value" of an assignment is equal to the value being assigned. Which means that max = nums[0] evaluates to the same value as nums[0]. So the line of code could be rewritten like this to make the meaning slightly more obvious:

min = (max = nums[0]);

And why this is done is simple: the "current minimum" and "current maximum" is often set to the first value of a non-empty list before the loop, because we know that the true minimum is at most as much as the value of the first element and the true maximum is at least as much as the value of the first element.

CodePudding user response：

Why do we initially set min and max to the first value in the array when trying to find the minimum and maximum value?

You don't have to set min and max to the first value. It is simply a way to find the values more efficiently since they must be one of those values so simply assign the first one. So you just assume that they are both min and max and the proceed to start with the next value in the array and alter min and max accordingly.

min = max = nums[0];
for (int i = 1; i < 10 ; i  ){
       if (nums[i] < min) min = nums[i];
       if (nums[i] > max) max = nums[i];
}

You could also do it like this.

min = Integer.MAX_VALUE;
max = Integer.MIN_VALUE;
for (int v : nums) {
   if (v < min) {
      min = v;
   }
   if (v > max) {
      max = v;
   }
}

In the above case, you are iterating over all the values so you can use the enhanced for loop. I also wrote it using curly braces for a single statement which, imo, is a good practice to help avoiding careless mistakes and inadvertently introducing bugs.

CodePudding user response：

It is the teacher's way of combining different aspects to see if you can understand all concepts that have already been taught.

It would be clearer to be more explicit and I would certainly iterate on all items instead of skipping the first item:

min = 0; // default min to 0
max = 0; // default max to 0
// iterate on ALL items in the array, starting at 0 till last element
for (int i = 0; i < nums.length ; i  ) {
    if (nums[i] < min) min = nums[i];
    if (nums[i] > max) max = nums[i];
}