使用 for 循环查找数组中的元素

Question

import java.util.Arrays;
import java.util.Scanner;

public class Grocer2 {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        String[] names = new String[5];
        int count = 0;
        while(true){
            System.out.println("What is your name: ");
            // Store scanner input in name
            String name = scan.nextLine();
            // Add name into array
            names[count] = name;
            count++;
            if(count == 5){
                break;
            }
        }
        System.out.println(Arrays.toString(names));
        while(true){
            System.out.println("Who are you looking for ? ");
            String contact = scan.nextLine();
            for(int i = 0; i < names.length; i++){
                if(names[i].equals(contact)){
                    System.out.println("They are in aisle " + i);
                }else{
                    System.out.println("Not here");
                }
            }
            break;
        }
        scan.close();
    }
}

我正在尝试将 Scanner 输入添加到数组中，并且我正在尝试使用 for 循环在数组中搜索元素。 for 循环遍历所有元素并在 names[i] 不等于 Scanner 输入时打印出“Not here”。我该如何解决这个问题？

Answer 1

while(true){
    System.out.println("Who are you looking for ? ");
    String contact = scan.nextLine();
    bool isFound = false;
    for(int i = 0; i < names.length; i++){
        if(names[i].equals(contact)){
            System.out.println("They are in aisle " + i);
            isFound = true;
            break;
        }
    }
    if(!isFound){
        System.out.println("Not here");
    }
    break;
}

Answer 2

如果你想让它只在你根本没有找到元素时不在这里打印，你应该把它放在 for 循环之后。因此，如果您找到名称说您找到了它，那么您将循环遍历整个数组，然后如果您没有找到，您可以在此处打印 not 类似这样的内容：

     while(true){
        System.out.println("Who are you looking for ? ");
        String contact = scan.nextLine();
       boolean isThere=false;
        for(int i = 0; i < names.length; i++){
             if(names[i].equals(contact)){
                 System.out.println("They are in aisle " + i);
                 isThere = true;
                 break;// break only if you want the first time the String appeared 
             }
         }
         if(!isThere){
          System.out.println("Not here");
         }
     break;
    }

现在应该可以了，但是这里的 while 循环没有做任何事情。考虑删除它或用它做其他事情，因为当你做第一个循环时，你是第一次直接中断，所以就好像根本没有循环一样。

Answer 3

你的第二个 while 循环永远不会循环。您可以在第一个循环中使用 do-while 循环。这是代码的更紧凑版本：

    Scanner scan = new Scanner(System.in);

    String[] names = new String[5];
    int count = 0;
    do {
        System.out.println("What is your name: ");
        // Add name into array
        names[count] = scan.nextLine();
        count++;
    } while (count != 5);

    System.out.println(Arrays.toString(names));

    System.out.println("Who are you looking for ? ");
    String contact = scan.nextLine();

    int aisle = -1;
    for(int i = 0; i < names.length; i++){
        if(names[i].equals(contact)){aisle = i; break;}
    }

    if (aisle != -1) System.out.println("They are in aisle " + aisle);
    else System.out.println("Not here");
    scan.close();

编辑：使用 ArrayList 而不是动态数组，这样做要容易得多。这是一个使用 ArrayLists 的版本：

    Scanner scan = new Scanner(System.in);

    ArrayList<String> names = new ArrayList<>(5);
    for (int i = 0; i<5; i++){
        System.out.println("What is your name: ");
        names.add(scan.nextLine());
    }
    System.out.println(names);

    System.out.println("Who are you looking for ? ");
    String contact = scan.nextLine();

    if (names.contains(contact)) System.out.println("They are in aisle " + names.indexOf(contact));
    else System.out.println("Not here");
    scan.close();

Answer 4

您可以创建一个名为 contactFound 的布尔值，并在找到匹配名称时将其设置为 true。发生这种情况时，您可能还想跳出循环。在 for 循环之外，如果 contactFound 为假，则打印 "Not here"，如下所示。

boolean contactFound = false;
for (int i = 0; i < names.length; i++) {
    if (names[i].equals(contact)) {
        System.out.println("They are in aisle " + i);
        contactFound = true;
        break; // If you want the loop to stop when a matching name has been found
    }
}
if (!contactFound) System.out.println("Not here");

Answer 5

import java.util.Arrays;
import java.util.Scanner;

public class Grocer2 {
    public static void main(String[] args) {

        int count = 0;
        int size = 5;

        //you should check here
        boolean check = false;

        Scanner scan = new Scanner(System.in);
        String[] names = new String[size];

        for (int i = 0; i<size; i++) {

            System.out.println("What is your name: ");
            // Store scanner input in name

            String name = scan.nextLine();
            // Add name into array

            names[count] = name;
            count++;

            if (count == size) {
                break;
            }
        }

        System.out.println(Arrays.toString(names));
        System.out.println("Who are you looking for ? ");
        String contact = scan.nextLine();

        for (int i = 0; i<names.length; i++) {
            if (names[i].equals(contact)) {
                System.out.println("They are in aisle " + i);
                check = true;
                break;
            }
        }
        if (!check) {
            System.out.println("Not here");
        }
        scan.close();
    }
}

使用 for 循环查找数组中的元素

Finding elements in array using for loop

java

arrays

for-loop

java.util.scanner