java 学生阵列菜单
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Student Array menu
提问by Liquified
I'm coding a menu to store names into an array, then giving options to add/delete students and search for a particular student as well, but I cant seem to find out how to set the array so that I can use it in other options, cause, for example, my code only allows me to input names when I use option 1, but it doesnt keep these names in the array when I choose option 3 to search for a name within the array, it just shows up as null for every slot in the array.
我正在编写一个菜单来将姓名存储到一个数组中，然后提供添加/删除学生和搜索特定学生的选项，但我似乎无法找到如何设置数组以便我可以在其他情况下使用它选项，例如，我的代码只允许我在使用选项 1 时输入名称，但是当我选择选项 3 在数组中搜索名称时，它不会将这些名称保留在数组中，它只显示为 null对于数组中的每个插槽。
Another problem I am having is about how I can delete students, obviously it would be really easy if the name is at the end of the array but what if the name is in the middle, how would I be able to delete the name, shift all the other names down one slot so that there are no gaps in the array?
我遇到的另一个问题是关于如何删除学生，显然如果名称在数组的末尾会很容易，但是如果名称在中间，我将如何删除名称，移位所有其他名称都在一个插槽中，以便阵列中没有间隙？
import java.util.Scanner;
public class Lab10Ex2 {
public static void main(String[] args) {
int choice = 0;
int[] stringArray = {};
do{
String[] stringarray = new String[20];
System.out.println("----------------MENU---------------");
System.out.println();
System.out.println("1. Add Students");
System.out.println("2. Delete Students");
System.out.println("3. Search for student");
System.out.println("4. Print all Students");
System.out.println("5. exit");
Scanner scanchoice = new Scanner(System.in);
choice = scanchoice.nextInt();
if (choice ==1){
Scanner scannames = new Scanner(System.in);
System.out.println("Please enter the student names into the array");
int i = 0;
for(i = 0; i<stringarray.length; i++){
String temp =scannames.nextLine();
stringarray[i]=temp.toLowerCase();
if(i==(stringarray.length-1)){
System.out.println("successfully filled up array fully");
System.out.println();
}
}
}
if(choice==2){
}
if(choice==3){
for(int p = 0; p<stringarray.length; p++){
System.out.println(stringarray[p]);
}
int x=0;
Scanner scannames1 = new Scanner(System.in);
System.out.println("Enter name of student you want to search for: ");
System.out.println();
String search=scannames1.nextLine();
String searchName=search.toLowerCase();
for(int p=0;p<20;p++){
if(searchName.equals(stringarray[p])){
x=1;
}
else{
x=0;
}
}
if(x==1){
System.out.println("We have a match in our database for "+ searchName);
}
else if (x==0){
System.out.println("No match for "+ searchName);
}
}
if (choice ==4){
System.out.println("List of names:");
for(int p = 0; p<stringarray.length; p++){
System.out.println(stringarray[p]);
}
}
}while(choice!=5);
}
}
采纳答案by Rafay
Here is the corrected code:
这是更正后的代码：
import java.util.Scanner;
public class Lab10Ex2 {
/**
* @param args
*/
public static void main(String[] args) {
int choice = 0;
int[] stringArray = {};
String[] stringarray = new String[20];
do{
System.out.println("----------------MENU---------------");
System.out.println();
System.out.println("1. Add Students");
System.out.println("2. Delete Students");
System.out.println("3. Search for student");
System.out.println("4. Print all Students");
System.out.println("5. exit");
Scanner scanchoice = new Scanner(System.in);
choice = scanchoice.nextInt();
if (choice ==1){
Scanner scannames = new Scanner(System.in);
System.out.println("Please enter the student names into the array");
System.out.println();
int i = 0;
for(i = 0; i<stringarray.length; i++){
String temp =scannames.nextLine();
stringarray[i]=temp.toLowerCase();
if(i==(stringarray.length-1)){
System.out.println("successfully filled up array fully");
System.out.println();
}
}
}
if(choice==2){
}
if(choice==3){
for(int p = 0; p<stringarray.length; p++){
System.out.println(stringarray[p]);
}
int x=0;
Scanner scannames1 = new Scanner(System.in);
System.out.println("Enter name of student you want to search for: ");
System.out.println();
String search=scannames1.nextLine();
String searchName=search.toLowerCase();
for(int p = 0; p < stringarray.length ;p++){
if(searchName.equals(stringarray[p])){
x=1;
break;
}
else{
x=0;
}
}
if(x==1){
System.out.println("We have a match in our database for "+ searchName);
}
else if (x==0){
System.out.println("No match for "+ searchName);
}
}
if (choice ==4){
System.out.println("List of names:");
for(int p = 0; p<stringarray.length; p++){
System.out.println(stringarray[p]);
System.out.println();
}
}
}while(choice!=5);
}
}
Things you were doing wrong:
你做错的事情：
- Instantiating the array in the do while loop.
- Not breaking out of the loop if a search entity was found in the array.
- 在 do while 循环中实例化数组。
- 如果在数组中找到搜索实体，则不会跳出循环。
Use ArrayList if you want to avoid wasting space in arrays after deletion. If you are bound to this with simple arrays, you can do this:
如果您想避免在删除后浪费数组空间，请使用 ArrayList。如果你用简单的数组绑定到这个，你可以这样做：
Place null at index from which you deleted.Create a temporary array with same size as the original one with all null values. Copy all the elements from the original array to the temporary one but skip elements that are null. Point the original array to the new array.
将空值放在从中删除的索引处。创建一个与原始数组大小相同的临时数组，其中包含所有空值。将原始数组中的所有元素复制到临时数组中，但跳过为空的元素。将原始数组指向新数组。
AND AVOID HARD CODING ARRAY LENGTHS!
并避免硬编码阵列长度！
回答by Jim Garrison
int choice = 0;
int[] stringArray = {};
do{
String[] stringarray = new String[20];
Delete the int[] stringArrayline (you don't refer to it anywhere).
删除该int[] stringArray行（不要在任何地方引用它）。
Move the String[] stringarrayup, outside the loop.
向上移动String[] stringarray，在循环之外。
As to deleting, you either have to code that yourself (move everything past the deleted item up one in the array), or use one of the collection classes provided with Java (instead of a native array), which handle deletion for you.
至于删除，您要么自己编写代码（将所有内容从数组中的已删除项上移一个），要么使用 Java 提供的集合类之一（而不是本机数组），它会为您处理删除。
回答by David Kirby
do{
String[] stringarray = new String[20];
On each iteration of your Do { ... } loop, you're recreating the stringarray variable, thus clearing it. If you move this outside of the loop, your student entries will be maintained.
在 Do { ... } 循环的每次迭代中，您都在重新创建 stringarray 变量，从而将其清除。如果您将其移到循环之外，您的学生条目将被保留。
As for deleting, if you're not required to use an array of strings, I would recommend using an ArrayList. It will allow you to easily remove specific entries without worrying about the other entries. Otherwise, yes, the simplest thing to do would be to move all of the other entries down one slot to avoid gaps
至于删除，如果您不需要使用字符串数组，我建议使用 ArrayList。它将允许您轻松删除特定条目，而无需担心其他条目。否则，是的，最简单的做法是将所有其他条目向下移动一个插槽以避免出现间隙
