線性查找

package lesson.l7_array;/*** Illustration** @author DengQing* @version 1.0* @datetime 2022/6/23 14:19* @function 線性查找*/
public class LineSearch {public static void main(String[] args) {String[]str={"AA","BB","CC"};boolean flag=false;String dest="BB";for (int i = 0; i < str.length; i++) {if (dest.equals(str[i])){System.out.println("已找到元素"+dest+",位置為"+i);flag=true;break;}}if (!flag){System.out.println("沒有找到元素"+dest);}}
}

線性查找-方式2

public class LineSearch2 {public static void main(String[] args) {String[]str={"AA","BB","CC"};String dest="DD";int i;for (i = 0; i < str.length; i++) {if (dest.equals(str[i])){System.out.println("已找到元素"+dest+",位置為"+i);break;}}if (i==str.length){System.out.println("沒有找到元素"+dest);}}
}

二分查找

注意點：二分查找是與中間值做比較

package lesson.l7_array;/*** Illustration** @author DengQing* @version 1.0* @datetime 2022/6/23 14:43* @function 二分查找：數組必須有序*/public class BinarySearch {public static void main(String[] args) {int[] arr = {1, 2, 3, 4, 5, 10, 20, 100};int dest = 10;int left = 0;int right = arr.length;boolean flag = false;while (left <= right) {int middleIndex = (left + right) / 2;int middle = arr[middleIndex];if (dest == middle) {System.out.println("已找到" + dest);flag = true;break;
//                往前找} else if (dest < middle) {right = middleIndex - 1;
//                往后找} else {left = middleIndex + 1;}}if (!flag) {System.out.println("沒有找到" + dest);}}
}