我从JavaFX开始，遇到了令人沮丧的运行时错误。我试图寻找解决方案和以前的答案，但我所看到的只是与fxml相关的东西。我什至不知道那是什么。我希望有人能够弄清楚是怎么回事。这是最严重的运行时错误。
代码如下：
package GUI;
import java.util.ArrayList;
import java.util.Arrays;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import java.util.Collection;
import java.util.Collections;
public class cw4 extends Application{
Button B1,B2,B3;
TextField TF1;
public static void main(String[] args) {
launch(args);
}
@Override
public void start(Stage window) throws Exception {
window.setTitle("Sorting UGs");
ArrayList<Student> students = new ArrayList<Student>();
ArrayList<Student> students2 = new ArrayList<Student>();
Student s1 = new Student(20007,3.8);
Student s2 = new Student(20002,3.4);
Student s3 = new Student(20003,3.5);
Student s4 = new Student(20004,3.6);
Student s5 = new Student(20005,3.7);
students.add(s1);
students.add(s2);
students.add(s3);
students.add(s4);
students.add(s5);
students2 = SortByGPA(students);
String str1 = students2.toString();
B1 = new Button ("Sort By ID");
B2 = new Button ("Sort By GPA");
B3 = new Button ("Clear");
TF1 = new TextField( "ID \t\t GPA\n" + students.toString());
HBox Box1 = new HBox(10);
Box1.getChildren().addAll(B1,B2,B3,TF1);
B1.setOnAction(e -> {
Collections.sort(students);
TF1 = new TextField( "ID \t\t GPA\n" + students.toString() );
});
B2.setOnAction(e -> {
TF1 = new TextField ( "ID \t\t GPA\n" + str1 );
});
B3.setOnAction(e -> {
TF1 = new TextField( "ID \t\t GPA\n" );
});
Scene S1 = new Scene(Box1);
window.setScene(S1);
window.show();
}
public static ArrayList<Student> SortByGPA(ArrayList<Student> students) {
for (int i = 0 ; i < students.size() ; i++)
for (int j = 0 ; j < students.size() ; j++) {
if (students.get(i).getGPA() > students.get(j).getGPA()) {
Student temp1 = students.get(i);
Student temp2 = students.get(j);
students.remove(i); // remove first element
students.remove(i); // second element became the first element so remove first element again
students.add(i,temp2);
students.add(i+1,temp1);
}
}
return students;
}
}
class Student implements Comparable<Student>{
private int id;
private double GPA;
public Student(int id, double gPA) {
this.id = id;
GPA = gPA;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public double getGPA() {
return GPA;
}
public void setGPA(double gPA) {
GPA = gPA;
}
@Override
public String toString() {
return id + "\t\t" + GPA + "\n" ;
}
@Override
public int compareTo(Student o) {
return this.id - o.getId();
}
}
谢谢！!!这是整个StackTrace：
Exception in Application start method
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.launcher.LauncherHelper$FXHelper.main(Unknown Source)
Caused by: java.lang.RuntimeException: Exception in Application start method
at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$155(LauncherImpl.java:182)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.IndexOutOfBoundsException: Index: 4, Size: 4
at java.util.ArrayList.rangeCheck(Unknown Source)
at java.util.ArrayList.remove(Unknown Source)
at cw4.cw4.SortByGPA(cw4.java:100)
at cw4.cw4.start(cw4.java:49)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
... 1 more
Exception running application cw4.cw4
答案 0 :(得分：1)
问题出在您的students.remove(i);语句上。
您正试图从列表中删除循环结束后不再存在的元素。您本质上是试图两次从列表中删除最后一个学生...
但是，您的代码还有其他几个问题。例如，您要在所有按钮的TextField属性中创建一个新的onAction()。这不会更新屏幕上的文本。您已经有一个TextField，因此要更改其内容，只需使用setText()方法：
TF1.setText("ID \t\t GPA\n");
您也不会通过简单地调用String来获得学生名单的有效toString()表示。
您需要重新考虑设计。
答案 1 :(得分：1)
似乎您的错误在于按GPA排序而不是JavaFX本身。我重写了如下所示的类，这将导致按GPA升序返回列表。如果希望它下降，则可以在students2上使用方法.reverse()。您收到的特定错误文本指出了OutofBounds错误，该错误是由您一次比较两个学生而不检查列表范围的方式引起的。解决此问题将导致您清除错误并运行代码，尽管Zephyr指出，其余代码的实现还需要解决其他问题。
public static ArrayList<Student> SortByGPA(ArrayList<Student> students)
{
students.sort(compareGPA());
return students;
}
private static Comparator<Student> compareGPA()
{
return new Comparator<Student>()
{
@Override
public int compare(Student s1, Student s2)
{
double gpa1 = s1.getGPA();
double gpa2 = s2.getGPA();
return Double.compare(gpa1, gpa2);
}
};
}