我有一类三个字段，两个int和一个double。我已经列出了我的类对象，并希望使用Scanner，BufferedReader和FileReader从文本文件中逐行读取数组的对象。
MWE：
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
public class Model {
public static final int Y = 7;
public static final int K = 42;
public static final int G = 3;
public static class Sleg {
// private int id;
private int i;
private int j;
private double l;
public Sleg(int i, int j, double l) {
// this.id = id;
this.i = i;
this.j = j;
this.l = l;
}
@Override
public String toString() {
return Integer.toString(i) + " " + Integer.toString(j) + " " + Double.toString(l);
}
}
public static void dataGen() {
System.out.print("slegs = ");
/*List<Sleg> slegs = Arrays.asList(); I want to write it like this and
read it from slFile.txt instead of the following line where the slegs are put one by one.*/
List<Sleg> slegs = Arrays.asList(new Sleg(1,2,400),new Sleg(2,5,800),new Sleg(5,7,450),new Sleg(2,3,800),new Sleg(3,6,500),new Sleg(3,4,500),new Sleg(4,5,500),new Sleg(7,5,450),new Sleg(5,4,500),new Sleg(4,3,400),new Sleg(6,3,550),new Sleg(3,2,700),new Sleg(2,1,400), new Sleg(5,2,800));
System.out.print(slegs);
System.out.println("]");
System.out.print("slegs = [");
for (Sleg s : slegs) {
System.out.print(s);
}
System.out.println("]");
System.out.print("slegs = [");
Sleg list2[] = new Sleg[slegs.size()];
list2 = slegs.toArray(list2);
File slFile = new File("slFile.txt");
try {
Scanner in7 = new Scanner(new BufferedReader(new FileReader("slFile.txt")));
while(in7.hasNextLine()) {
for (int sl = 0; sl < list2.length; sl++) {
String[] line = in7.nextLine().trim().split(" ");
list2[sl] = Double.parseDouble(line);
}
}
} catch (FileNotFoundException e) {
System.out.println("Unable to read : " + slFile.toString());
}
for (Sleg i : list2) {
System.out.print(i);
}
System.out.println("]");
System.out.print("slegs = [");
Object[] ss = slegs.toArray();
for (int i = 0; i < ss.length; i++) {
System.out.print(ss[i]);
}
System.out.println("]");
int[][] u = new int [slegs.size()][G];
}
}
数据：
1 2 400
2 5 800
5 7 450
2 3 800
3 6 550
3 4 500
4 5 500
7 5 450
5 4 500
4 3 400
6 3 550
3 2 700
2 1 400
5 2 800
但是，弹出错误“将行更改为String”。如果我有一个3维数组，而不是包含3个字段的Sleg类的slegs对象，我知道如何读取文件，但是对此，我没有任何想法。 非常感谢您的想法！
答案 0 :(得分：1)
您提供的代码存在一些问题。您尝试将#include <iostream>
#include <vector>
std::string build() {
std::vector<std::string> data;
data.push_back("One");
data.push_back("1");
const std::string token = "%s";
const std::string description = "This %s is number %s";
std::string out = "";
size_t start = 0;
size_t end = description.find(token);
int i = 0;
while (end != std::string::npos) {
out += description.substr(start, end - start);
out += data[i++];
start = end + token.length();
end = description.find(token, start);
}
out += description.substr(start, end - start);
return out;
}
int main () {
std::cout << build() << '\n';
return 0;
}
与This One is number 1
一起使用，假设文本文件中的行数，Boolean.parseBoolean(String)变量的类型为String[]，但您重新尝试为其元素和其他各种事物分配一个list2。
假设您只是想将文件读入Sleg[]对象的列表中，则可能需要执行以下操作：
double答案 1 :(得分：1)
好吧，我使用LinkedList是因为我不知道那里有多少个项目/行（我本可以算出它们，但是如果没有指示有多少行，即第一行指示项目数） ...我将使用链接列表）。现在，您的方法dataGen将返回一个LinkedList存储Sleg对象的对象。这是有效的MVCE：
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.LinkedList;
import java.util.Scanner;
public class Model {
public static final int Y = 7;
public static final int K = 42;
public static final int G = 3;
public Model() {
dataGen();
}
public LinkedList<Sleg> dataGen() {
LinkedList<Sleg> data = new LinkedList<>();
File slFile = new File("slFile.txt");
try {
Scanner in7 = new Scanner(new BufferedReader(new FileReader("slFile.txt")));
while (in7.hasNextLine()) {
//get current line and split it via a space.
String[] split = in7.nextLine().split(" ");
int x = Integer.parseInt(split[0]);
int y = Integer.parseInt(split[1]);
double z = Double.parseDouble(split[2]);
Sleg newItem = new Sleg(x, y, z);//new entry.
data.add(newItem);//add as an entry to data.
}
in7.close();//should have this!!!
} catch (FileNotFoundException e) {
System.out.println("Unable to read : " + slFile.toString());
}
for (Sleg current : data) {
System.out.println(current.toString());
}
return data;
}
public static void main(String[] args) {
new Model();
}
class Sleg {
int x = 0;
int y = 0;
double z = 0;
Sleg(int x, int y, double z) {
this.x = x;
this.y = y;
this.z = z;
}
@Override
public String toString() {
return "(" + x + ", " + y + ", " + z + ")";
}
}
}
答案 2 :(得分：1)
问题在这里：
Double.parseDouble(line)您无法将字符串数组解析为双精度型：Sleg。
您也不能为对象引用分配双精度字（即：list2[sl] = Double.parseDouble(line)）：String[] line = in7.nextLine().trim().split(" ");。
读取下一行的操作应放在外部while循环中：for。
list2循环是不必要的，因为每个循环周期只处理一个元素（不是int sl = 0;
while(in7.hasNextLine() && sl < list2.length) {
String[] line = in7.nextLine().trim().split(" ");
if (line.length < 3) {
System.out.println("invalid line: " + line);
continue;
}
list2[sl] = new Sleg(
Integer.parseInt(line[0]),
Integer.parseInt(line[1]),
Double.parseInt(line[2])
);
sl++;
}
中的所有元素）。
基于上述内容，可以将其修改为：
create type Customer_t as object(
cid char(6),
cusname varchar(15),
birthdate date,
phone char(10),
address varchar(50)
);
create type claim_t as object(
claimno char(12),
cdate date,
amount number(8,2),
claimant ref customer_t
);
create type Claim_ntab is table of claim_t;
create type policy_t as object(
pid char(7),
sdate date,
edate date,
inscar ref car_t,
premium number(6,2),
claims claim_ntab
);
create table Policies of policy_t(
pid primary key,
inscar references Cars
)nested table claims store as claims_ntable;