使用scanner在ArrayList的ArrayList中加载Java
我尝试使用scanner加载模块的ArrayList,然后每个模块还包含一个注册该模块的学生的ArrayList。这是我的模块构造函数:使用scanner在ArrayList的ArrayList中加载Java,java,arraylist,load,Java,Arraylist,Load,我尝试使用scanner加载模块的ArrayList,然后每个模块还包含一个注册该模块的学生的ArrayList。这是我的模块构造函数: public Module(String newCode, ArrayList<Student> students){ } 我已经能够使用扫描仪加载学生,如下所示: public void loadStudents(String fileName) throws FileNotFoundException{ Scanner inf
public Module(String newCode, ArrayList<Student> students){
}
我已经能够使用扫描仪加载学生,如下所示:
public void loadStudents(String fileName) throws FileNotFoundException{
Scanner infile =new Scanner(new InputStreamReader
(new FileInputStream(fileName)));
int num=infile.nextInt();infile.nextLine();
for (int i=0;i<num;i++) {
String u=infile.nextLine();
String s=infile.nextLine();
String n=infile.nextLine();
String c=infile.nextLine();
Student st = new Student(u,s,n,c);
students.add(st);
}
infile.close();
}
public void loadStudents(字符串文件名)引发FileNotFoundException{
扫描仪内嵌=新扫描仪(新InputStreamReader
(新文件输入流(文件名));
int num=infle.nextInt();infle.nextLine();
for(int i=0;iinfle.next()
返回一个字符串
值,因此它不能填充ArrayList
。从文本文件填充ArrayList
的一般方法如下:
public ArrayList<ArrayList<String>> readFile(String filename) throws IOException
{
FileInputStream fis = new FileInputStream(filename);
Scanner sc = new Scanner(fis);
ArrayList<ArrayList<String>> modulesList = new ArrayList<>();
int numModules = sc.nextInt();
for (int i = 0; i < numModules; i++)
{
int numStringsPerModule = sc.nextInt();
ArrayList<String> moduleEntries = new ArrayList<>();
for (int j = 0; j < numStringsPerModule; j++)
{
String entry = sc.next();
moduleEntries.add(entry);
}
modulesList.add(moduleEntries);
}
return modulesList;
}
public ArrayList readFile(字符串文件名)引发IOException
{
FileInputStream fis=新的FileInputStream(文件名);
扫描仪sc=新扫描仪(fis);
ArrayList modulesList=新的ArrayList();
int numModules=sc.nextInt();
for(int i=0;i
您应该能够根据您的具体情况定制此代码。一般的想法是,您需要为
循环使用嵌套的,内部循环在单个模块中读取。以下内容如何
public ArrayList<Student> loadStudents(Scanner infile) throws FileNotFoundException{
ArrayList<Student> students = new ArrayList<Student>();
int num=infile.nextInt();infile.nextLine();
for (int i=0;i<num;i++) {
String u=infile.nextLine();
String s=infile.nextLine();
String n=infile.nextLine();
String c=infile.nextLine();
Student st = new Student(u,s,n,c);
students.add(st);
}
return studtends;
}
public ArrayList loadStudents(Scanner infle)抛出FileNotFoundException{
ArrayList students=新ArrayList();
int num=infle.nextInt();infle.nextLine();
对于(int i=0;i您确定要复制粘贴相同的代码吗?因为ArrayList a=infle.next()这一行无法编译。是的,这就是问题所在。这是我试图让它工作的尝试,但显然不起作用。请正确复制粘贴loadModules
代码。这就是我对loadModules的所有功能,我不知道它应该是什么样子。我怀疑。我更喜欢使用方法来解析子结构我尝试了原始海报。仍然会有一个内部for循环;它只是隐藏在一个方法调用中。我是从算法的角度讲的,而不是从语义的角度讲的。big-O仍然是一样的。
public ArrayList<ArrayList<String>> readFile(String filename) throws IOException
{
FileInputStream fis = new FileInputStream(filename);
Scanner sc = new Scanner(fis);
ArrayList<ArrayList<String>> modulesList = new ArrayList<>();
int numModules = sc.nextInt();
for (int i = 0; i < numModules; i++)
{
int numStringsPerModule = sc.nextInt();
ArrayList<String> moduleEntries = new ArrayList<>();
for (int j = 0; j < numStringsPerModule; j++)
{
String entry = sc.next();
moduleEntries.add(entry);
}
modulesList.add(moduleEntries);
}
return modulesList;
}
public ArrayList<Student> loadStudents(Scanner infile) throws FileNotFoundException{
ArrayList<Student> students = new ArrayList<Student>();
int num=infile.nextInt();infile.nextLine();
for (int i=0;i<num;i++) {
String u=infile.nextLine();
String s=infile.nextLine();
String n=infile.nextLine();
String c=infile.nextLine();
Student st = new Student(u,s,n,c);
students.add(st);
}
return studtends;
}
public List<Module> loadModules(String fileName) throws FileNotFoundException{
Scanner infile =new Scanner(new InputStreamReader
(new FileInputStream(fileName)));
int num=infile.nextInt();infile.nextLine();
List<Module> ret = List<Module>();
for (int i=0;i<num;i++){
String c=infile.nextLine();
ArrayList<Student> a =loadStudents(infile);
Module m = new Module(c,a);
ret.add(m);
}
infile.close();
return ret;
}