所以我有一个正在制作摔跤支架的程序，我让它从CSV文件中获取输入。
Alex,Brown,School1,140,10,2,12,10
Bill,Bob,School2,140,8,4,9,3
Ted,Red,School1,140,12,5,5,9
Randy,Ted,School2,140,17,7,10,8
Sam,Mark,School2,140,21,4,10,8
Noel,Frank,School2,140,7,8,10,8
然而，当我让扫描仪通过时，它会完成所有操作，并且由于某种原因，调试输出在名字之间打印出零，然后不会停止，即使while循环设置为停止当hasNext（）方法返回false时。
我的代码：
import java.util.ArrayList;
import java.util.Collections;
import java.lang.Object;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class Bracket_Creator{
public static void main(String[] args) throws FileNotFoundException
{
String first_name = "";
String last_name = "";
String school = "";
int weight = 0;
int confer_win = 0;
int confer_loss = 0;
int overall_wins = 0;
int overall_loss = 0;
ArrayList<Wrestler> list = new ArrayList<Wrestler>();
int i = 0;
boolean flag = true;
//new scanner instance
Scanner scanner = new Scanner(new File("wrestlers.csv"));
//the seperator for the file
scanner.useDelimiter(",");
while(scanner.hasNext()){
first_name = scanner.next();
last_name = scanner.next();
school = scanner.next();
weight = scanner.nextInt();
confer_win = scanner.nextInt();
confer_loss = scanner.nextInt();
overall_wins = scanner.nextInt();
overall_loss = scanner.nextInt();
list.add(new Wrestler(first_name,last_name,school,weight,
confer_win,confer_loss,overall_wins,overall_loss));
System.out.println((list.get(i).get_first_name()));
i++;
}//end while
scanner.close();
//make the percentages for the wrestlers
for (i = 0; i < list.size(); i++){
(list.get(i)).determine_conf_percentage((list.get(i)).get_confer_wins(), (list.get(i)).get_confer_losses());
(list.get(i)).determine_overall_percentage((list.get(i)).get_overall_wins(), (list.get(i)).get_overall_losses());
}//end for loop
//set rank
while ( flag )
{
flag= false; //set flag to false awaiting a possible swap
for( i=0; i < list.size() -1; i++ )
{
if ((list.get(i)).get_confer_percentage() < (list.get(i+1)).get_confer_percentage() )
{
Collections.swap(list, i, i+1);
flag = true;
}//end if
}//end for
}//end while
//set rank value
for (i = 0; i< list.size(); i++){
(list.get(i)).set_rank(i + 1);
}//end for loop
for (i = 0; i< list.size(); i++){
System.out.println((list.get(i)).get_first_name());
}
System.out.println("");
/*
*
*
*Create the Bracket!
*
*
*/
int j = 1; //J here is for the end of the list, every time you go through
//add one to J in the loop to keep on coming in from the other end of
//the list
for (i = 0; i< (list.size()/2); i++){
if (i == 0) {//first pass thru the list
System.out.println((list.get(i)).get_first_name());
System.out.println((list.get(list.size()-j)).get_first_name());
System.out.println();
j++;
}//end if
else{
System.out.println((list.get(i)).get_first_name());
System.out.println((list.get(list.size()-j)).get_first_name());
System.out.println();
j++;
}//end else
}//end for
}//end main
}//end bracket_creator class
这是Wrestler类代码，供参考：
public class Wrestler {
private String first_name = "";
private String last_name = "";
private String school = "";
private int weight_class = 0;
private int confer_wins = 0;
private int confer_losses = 0;
private int overall_wins = 0;
private int overall_losses = 0;
private double confer_percentage = 0;
private double overall_percentage = 0;
private int rank;
/* Constructors! */
public Wrestler(String init_first_name, String init_last_name,
String init_school, int init_weight_class, int init_confer_wins,
int init_confer_losses, int init_overall_wins, int init_overall_losses) {
first_name = init_first_name;
last_name = init_last_name;
school = init_school;
weight_class = init_weight_class;
confer_wins = init_overall_wins;
confer_losses = init_confer_losses;
overall_wins = init_overall_wins;
overall_losses = init_overall_losses;
confer_percentage = 0;
overall_percentage = 0;
rank = 0;
}//end wresler constructor
/*
*
*
* setters
*
*/
public void set_first_name(String new_first_name){
first_name = new_first_name;
}//end first name setter
public void set_last_name(String new_last_name){
last_name = new_last_name;
}//end last name setter
public void set_school(String new_school){
school = new_school;
}//end school setter
public void set_weight_class(int new_weight_class){
weight_class = new_weight_class;
}//end weight class setter
public void set_conf_wins(int new_conf_wins){
confer_wins = new_conf_wins;
}//end conference wins setter
public void set_conf_losses(int new_conf_losses){
confer_losses = new_conf_losses;
}//end conference losses setter
public void set_over_wins(int new_over_wins){
overall_wins = new_over_wins;
}//end over wins setter
public void set_over_losses(int new_over_losses){
overall_losses = new_over_losses;
}//end over losses setter
public void set_confer_percentage(double new_confer_percentage){
confer_percentage = new_confer_percentage;
}//end conference percentage setter
public void set_overall_percentage(double new_overall_percentage){
overall_percentage = new_overall_percentage;
}//end overall percentage setter
public void set_rank(int new_rank){
rank = new_rank;
}//end rank setter
/*
*
*
* Getters
*
*/
public String get_first_name(){
return first_name;
}//end first name
public String get_last_name(){
return first_name;
} //end last name
public String get_school(){
return school;
}
public int get_weight_class(){
return weight_class;
}//end weight class
public int get_confer_wins(){
return confer_wins;
}
public int get_confer_losses(){
return confer_losses;
}
public int get_overall_wins(){
return overall_wins;
}
public int get_overall_losses(){
return overall_losses;
}
public double get_confer_percentage(){
return confer_percentage;
}
public double get_overall_percentage(){
return overall_percentage;
}
public int get_rank(){
return rank;
}
public void determine_conf_percentage(int confer_wins, int confer_losses){
double determined_percentage = 0;
if (confer_losses + confer_wins < 4){
set_confer_percentage(determined_percentage);
}
else {
//note: the 1.0 converts the ints to doubles.
determined_percentage = 100 * ((1.0*confer_losses) / ((1.0*confer_wins) + (1.0 * confer_losses)));
set_confer_percentage(determined_percentage);
}
}// end determine_conf_percetnage
public void determine_overall_percentage(int overall_wins, int overall_losses){
double determined_percentage = 0;
if (overall_losses + overall_wins < 4){
set_overall_percentage(determined_percentage);
}
else {
//note: the 1.0 converts the ints to doubles.
determined_percentage = 100 * ((1.0*overall_losses) / ((1.0*overall_wins) + (1.0 * overall_losses)));
set_overall_percentage(determined_percentage);
}
}// end determine_conf_percetnage
}//end Wrestlerpublic class Wrestler {
private String first_name = "";
private String last_name = "";
private String school = "";
private int weight_class = 0;
private int confer_wins = 0;
private int confer_losses = 0;
private int overall_wins = 0;
private int overall_losses = 0;
private double confer_percentage = 0;
private double overall_percentage = 0;
private int rank;
/* Constructors! */
public Wrestler(String init_first_name, String init_last_name,
String init_school, int init_weight_class, int init_confer_wins,
int init_confer_losses, int init_overall_wins, int init_overall_losses) {
first_name = init_first_name;
last_name = init_last_name;
school = init_school;
weight_class = init_weight_class;
confer_wins = init_overall_wins;
confer_losses = init_confer_losses;
overall_wins = init_overall_wins;
overall_losses = init_overall_losses;
confer_percentage = 0;
overall_percentage = 0;
rank = 0;
}//end wresler constructor
/*
*
*
* setters
*
*/
public void set_first_name(String new_first_name){
first_name = new_first_name;
}//end first name setter
public void set_last_name(String new_last_name){
last_name = new_last_name;
}//end last name setter
public void set_school(String new_school){
school = new_school;
}//end school setter
public void set_weight_class(int new_weight_class){
weight_class = new_weight_class;
}//end weight class setter
public void set_conf_wins(int new_conf_wins){
confer_wins = new_conf_wins;
}//end conference wins setter
public void set_conf_losses(int new_conf_losses){
confer_losses = new_conf_losses;
}//end conference losses setter
public void set_over_wins(int new_over_wins){
overall_wins = new_over_wins;
}//end over wins setter
public void set_over_losses(int new_over_losses){
overall_losses = new_over_losses;
}//end over losses setter
public void set_confer_percentage(double new_confer_percentage){
confer_percentage = new_confer_percentage;
}//end conference percentage setter
public void set_overall_percentage(double new_overall_percentage){
overall_percentage = new_overall_percentage;
}//end overall percentage setter
public void set_rank(int new_rank){
rank = new_rank;
}//end rank setter
/*
*
*
* Getters
*
*/
public String get_first_name(){
return first_name;
}//end first name
public String get_last_name(){
return first_name;
} //end last name
public String get_school(){
return school;
}
public int get_weight_class(){
return weight_class;
}//end weight class
public int get_confer_wins(){
return confer_wins;
}
public int get_confer_losses(){
return confer_losses;
}
public int get_overall_wins(){
return overall_wins;
}
public int get_overall_losses(){
return overall_losses;
}
public double get_confer_percentage(){
return confer_percentage;
}
public double get_overall_percentage(){
return overall_percentage;
}
public int get_rank(){
return rank;
}
public void determine_conf_percentage(int confer_wins, int confer_losses){
double determined_percentage = 0;
if (confer_losses + confer_wins < 4){
set_confer_percentage(determined_percentage);
}
else {
//note: the 1.0 converts the ints to doubles.
determined_percentage = 100 * ((1.0*confer_losses) / ((1.0*confer_wins) + (1.0 * confer_losses)));
set_confer_percentage(determined_percentage);
}
}// end determine_conf_percetnage
public void determine_overall_percentage(int overall_wins, int overall_losses){
double determined_percentage = 0;
if (overall_losses + overall_wins < 4){
set_overall_percentage(determined_percentage);
}
else {
//note: the 1.0 converts the ints to doubles.
determined_percentage = 100 * ((1.0*overall_losses) / ((1.0*overall_wins) + (1.0 * overall_losses)));
set_overall_percentage(determined_percentage);
}
}// end determine_conf_percetnage
}//end Wrestler
答案 0 :(得分：0)
每次调用scanner.next（）之前都需要检查hasNext（） 所以你的 first_name = scanner.next（）
语句永远不会失败，但在执行此语句后，您不会检查scanner.hasNext（）
答案 1 :(得分：0)
您在csv
的末尾有一个额外的0
Alex,Brown,School1,140,10,2,12,10,0
这不应该被循环中的任何东西读取。
在第一次循环迭代中，它不会被读取，但在第二次循环时它将被
读取first_name = scanner.next();
因为分隔符是,。这一直持续到你仍然有
0
在缓冲区中，因此hasNext()将返回true。这将读取它
first_name = scanner.next（）;
然后
中没有任何内容last_name = scanner.next();
所以抛出了异常。
你可以做的就是添加一个简单的
scanner.nextInt()
在循环结束时。
答案 2 :(得分：0)
这看起来像是问题
//the seperator for the file
scanner.useDelimiter(",");
while(scanner.hasNext()){
first_name = scanner.next();
last_name = scanner.next();
school = scanner.next();
weight = scanner.nextInt();
confer_win = scanner.nextInt();
confer_loss = scanner.nextInt();
overall_wins = scanner.nextInt();
overall_loss = scanner.nextInt();
list.add(new Wrestler(first_name,last_name,school,weight,
confer_win,confer_loss,overall_wins,overall_loss));
System.out.println((list.get(i).get_first_name()));
i++;
hasNext（）只会检查是否存在其他分隔符，而不是所有9个下一次扫描都能正常工作。
答案 3 :(得分：0)
我刚刚这样做了：
import java.util.ArrayList;
import java.util.Collections;
import java.lang.Object;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;
public class Bracket_Creator{
public static void main(String[] args) throws FileNotFoundException
{
String first_name = "";
String last_name = "";
String school = "";
int weight = 0;
int confer_win = 0;
int confer_loss = 0;
int overall_wins = 0;
int overall_loss = 0;
ArrayList<Wrestler> list = new ArrayList<Wrestler>();
int i = 0;
boolean flag = true;
BufferedReader br = null;
String line = "";
String splitBy = ",";
//new scanner instance
try {
br = new BufferedReader(new FileReader("wrestlers.csv"));
while ((line = br.readLine()) != null){
String[] attributes = line.split(splitBy);
list.add(new Wrestler(attributes[0],attributes[1],attributes[2],
Integer.parseInt(attributes[3]),
Integer.parseInt(attributes[4]),
Integer.parseInt(attributes[5]),
Integer.parseInt(attributes[6]),
Integer.parseInt(attributes[7])));
}//end while
}//end try
catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (br != null){
try {
br.close();
} catch (IOException e){
e.printStackTrace();
}
}
}
//make the percentages for the wrestlers
for (i = 0; i < list.size(); i++){
(list.get(i)).determine_conf_percentage((list.get(i)).get_confer_wins(), (list.get(i)).get_confer_losses());
(list.get(i)).determine_overall_percentage((list.get(i)).get_overall_wins(), (list.get(i)).get_overall_losses());
}//end for loop
//set rank
while ( flag )
{
flag= false; //set flag to false awaiting a possible swap
for( i=0; i < list.size() -1; i++ )
{
if ((list.get(i)).get_confer_percentage() < (list.get(i+1)).get_confer_percentage() )
{
Collections.swap(list, i, i+1);
flag = true;
}//end if
}//end for
}//end while
//set rank value
for (i = 0; i< list.size(); i++){
(list.get(i)).set_rank(i + 1);
}//end for loop
for (i = 0; i< list.size(); i++){
System.out.println((list.get(i)).get_first_name());
}
System.out.println("");
/*
*
*
*Create the Bracket!
*
*
*/
int j = 1; //J here is for the end of the list, every time you go through
//add one to J in the loop to keep on coming in from the other end of
//the list
for (i = 0; i< (list.size()/2); i++){
if (i == 0) {//first pass thru the list
System.out.println((list.get(i)).get_first_name());
System.out.println((list.get(list.size()-j)).get_first_name());
System.out.println();
j++;
}//end if
else{
System.out.println((list.get(i)).get_first_name());
System.out.println((list.get(list.size()-j)).get_first_name());
System.out.println();
j++;
}//end else
}//end for
}//end main
}//end bracket_creator class
工作了，我有一个异常处理程序。