array

package array;

public class ArrayDemo01 {
    public static void main(String[] args) {
        int[] nums = null;
        nums = new int[5];
        int[] nums2 = new int[3];
        nums[0] = 1;
        nums[1] = 2;
        nums[2] = 3;
        nums[3] = 4;
        nums[4] = 5;
        System.out.println(nums[2]);
        System.out.println(nums2[2]);
        int sum = 0;
        for (int i = 0; i < nums.length; i++) {
            sum += nums[i];
        }
        System.out.println(sum);
    }
}

package array;

public class ArrayDemo02 {
    public static void main(String[] args) {
        int[] nums = {1,3,5,6,9};
        double[] nums3 = {1,3,5,6,9};
        Man[] mans = {new Man(),new Man()};
        System.out.println(nums[3]);
        System.out.println(mans[0]);
        System.out.println(nums);
        System.out.println(nums3);


        int[] nums2 = new int[4];
        int[] a = new int[5];
        a[1] = 2;
        a[3] = 3;
        nums2[0] = 9;
        nums2[1] = 3;
        System.out.println(nums2[0]);
        System.out.println(nums2[1]);
        System.out.println(nums2[2]);
        System.out.println(nums2[3]);
    }
}

package array;

public class Man {
}

package array;

public class ArrayDemo03 {
    public static void main(String[] args) {
        int[] array = {1,2,3,4,5};
        for (int i = 0; i < array.length; i++) {
            System.out.print(array[i]+" ");
        }
        System.out.print("\n");
        System.out.println("======================================");
        int sum = 0;
        for(int i=0;i<array.length;i++){
            sum += array[i];
        }
        System.out.println("sum = "+sum);
        System.out.println("===========================================");
        int max = array[0];
        for (int i=0;i<array.length;i++){
            if(array[i]>max){
                max = array[i];
            }
        }
        System.out.println(max);
    }



}

package array;

public class ArrayDemo04 {
    public static void main(String[] args) {
        int[] num = {1,3,5,7,9};
        for(int a : num){
            System.out.print(a+" ");
        }
        System.out.println();
        System.out.println("========================");
        double[] a = {1.1,1.5,1.3,1.7,1.9};
        printArray(a);
        System.out.println("========================");
        int[] reverse = reverse(num);
        printArray(reverse);
    }
    public static void printArray(double[] array){
        for (int i = 0; i < array.length; i++) {
            System.out.print(array[i]+" ");
        }
        System.out.println();
    }
    public static void printArray(int[] array){
        for (int i = 0; i < array.length; i++) {
            System.out.print(array[i]+" ");
        }
        System.out.println();
    }
    public static int[] reverse(int[] array){
        int[] result = new int[array.length];
        for(int i=0,j=result.length-1;i<array.length;i++,j--){
            result[j] = array[i];
        }
        return result;
    }
}