当我在 for 循环内迭代数组元素时，如何迭代 Java 中的数组元素？

Question

I am learning java and am learning arrays in Java. I wanted to try and make a program that goes through each element in the array and using a method the program sees if the elements are either increasing, decreasing, or part of the array is increasing and part of the array is decreasing. I am pretty confused on how to do this and would like some guidance on what I need to fix. I am guessing that my attempt is probably very far from what I wanted to have happen.

I am not really sure how to loop through the array and test each individual element. I attempted it but I did it incorrectly. I tried to make a for loop which would iterate through the elements of the array. Inside of the for loop I tried making an if statement and I wanted it to go through each element in the array and then check if the order of the array was in increasing order and then output "Increasing", decreasing order, and output "Decreasing", or if part of the array was increasing and part of it was decreasing I wanted the output to be "Increasing and decreasing". (example: {1,3,5,7,4,2} ) 1,3,5,7 increase and 4,2 is decreasing. So I have one loop to iterate through each element in the array and then another loop inside the first loop checking if the elements are increasing or decreasing in the array and outputting Increase or Decrease.

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

        int[] array1 = { 3, 8, 13, 29, 52, 81 };

        int[] array2 = { 77, 66, 55, 33, 22, 11 };

        int[] array3 = { 20, 30, 60, 40, 15, 2 };

        int[] array4 = { 10, 30, 50, 50, 60, 80 };

        // call the method
        increaseOrDecrease(array1);
        increaseOrDecrease(array2);
        increaseOrDecrease(array3);
        increaseOrDecrease(array4);
    }

    // create the method

    public static int increaseOrDecrease(int[] myArray) {
        // make a loop to check if all the integers of the array are in either
        // increasing or decreasing order or both


        for (int i = 0; i < myArray.length; i++) {

            // if the array is increasing
// What I wanted is for it to start at array i = 0 and have [i] go up by 1 until it loops through the end // of the array. Then if each element is less than the subsequent element it would output "Increasing": I // did not do this correctly and would like some help. I guess all I did is check if myArray[i] is less 
// than myArray[i+1]

// if the array was {1, 3, 6, 8} then the method would go through each element and find that index [0] < 
// index [1] and index[1] < index [2] and index[2] < index [3] and output Increasing and return a value of // 1 because the method would find that all the numbers are ordered smallest to largest.


            if (myArray[i] < myArray[i++]) {


                System.out.println("Increasing");
                return 1;
            }

// this is incorrect and does not do what I was hoping it would.
            // if the array is decreasing
            else if (myArray[i] > myArray[i++]) {
                System.out.println("Decreasing");
                return 2;
            }


// this is also incorrect
            // if the array is increasing and decreasing
            else (myArray[i] < myArray[i++] && myArray[i] > myArray[i++]) {
                System.out.println("Both increasing and decreasing");
                return 3;
            }
        }
        return 0;

    }

}

This is what I wanted: for each element check and see if the element is less than the next element in the array. For the first array {3,8,17,25,89,94} it would loop through the array. Index 0 is 3 which is less than index 1. It goes to element 1 which is 8 and index 1 is less than index 2 which is 17. This would keep happening until the method looped through all the elements in the array and it would output Increasing. If every element in the array is smaller than the subsequent elements checking if the order is smallest to largest then the method would output Increasing. Then I would do the same thing if the array is decreasing only in reverse. I did not do this correctly and would like some help, please.

Here is what I tried to do to check if the array is from smallest to largest. I think it just checked if [i] < [i++] but did not go through the entire array.

      for (int i = 0; i < myArray.length; i++) {

            // if the array is increasing
// What I wanted is for it to start at array i = 0 and have [i] go up by 1 until it loops through the end // of the array. Then if each element is less than the subsequent element it would output "Increasing": I // did not do this correctly and would like some help. I guess all I did is check if myArray[i] is less 
// than myArray[i+1]

// if the array was {1, 3, 6, 8} then the method would go through each element and find that index [0] < 
// index [1] and index[1] < index [2] and index[2] < index [3] and output Increasing and return a value of // 1 because the method would find that all the numbers are ordered smallest to largest.


            if (myArray[i] < myArray[i++]) {


                System.out.println("Increasing");
                return 1;
            }

Answer 1

public class Eli {
   
    public static void main(String[] args) {
        int myArray[] = {12,5,4,7,2};
        boolean increasing = false, decreasing = false;
        for (int i = 0; i < myArray.length-1; i++) {
            
            if (myArray[i] < myArray[i+1]) {
                increasing = true;
            }
            if (myArray[i] > myArray[i+1]) {
                decreasing = true;
            }

        }
        if (increasing == true && decreasing == true) {
            System.out.println("Increasing and decreasing");
        }
        else {
            if (increasing == true)
                System.out.println("Increasing");
            else System.out.println("Decreasing");
        }

    }
}

Note: If you make sure that a rise after a fall is not considered a "rise and fall", the first condition in the loop will be:

if (decreasing == true)
    break;