public class MaxProduct {public static int maxProduct(int[] arr) {if (arr == null || arr.length < 2) {return 0;}int max1 = Integer.MIN_VALUE, max2 = Integer.MIN_VALUE;int min1 = Integer.MAX_VALUE, min2 = Integer.MAX_VALUE;for (int num : arr) {if (num > max1) {max2 = max1;max1 = num;} else if (num > max2) {max2 = num;}if (num < min1) {min2 = min1;min1 = num;} else if (num < min2) {min2 = num;}}return Math.max(max1 * max2, min1 * min2);}
}
import org.junit.Test;
import static org.junit.Assert.*;public class MaxProductTest{@Testpublic void testMaxProduct1() {// 正数和负数混合int[] arr1 = {3, 5, -2, 8, -7};assertEquals(40, MaxProduct.maxProduct(arr1)); // 8*5}@Testpublic void testMaxProduct2() {// 全负数int[] arr2 = {-1, -4, -3, -2};assertEquals(12, MaxProduct.maxProduct(arr2)); // -4*-3}@Testpublic void testMaxProduct3() {// 全正数int[] arr3 = {1, 2, 3, 4};assertEquals(12, MaxProduct.maxProduct(arr3)); // 4*3}@Testpublic void testMaxProduct4() {// 只有一个元素int[] arr4 = {5};assertEquals(0, MaxProduct.maxProduct(arr4));}@Testpublic void testMaxProduct5() {// 空数组int[] arr5 = {};assertEquals(0, MaxProduct.maxProduct(arr5));}
}
