我正在完成学校的实验任务,并且在编译时出现此错误。该程序运行良好,有点想修复导致错误的原因。程序代码和完整的错误如下。一如既往的感谢!
错误:注意:F:\ Java \ Lab 8 \ Lab8.java使用未经检查或不安全的操作。注意:使用-Xlint:unchecked重新编译以获取详细信息。
码:
import java.awt.*; import java.awt.event.*; import javax.swing.*; import javax.swing.event.*; import javax.swing.border.*; public class Lab8 extends JFrame { public Lab8() { // Create an array of Strings for age ranges String[] ageRanges = {"Under 20", "20-29", "30-39", "40-49", "50-59", "60 and Above"}; JComboBox jcbo = new JComboBox(ageRanges); // Create an array of String destinations String[] destination = {"Mercury", "Venus", "Moon", "Mars", "Jupiter / Europa", "Saturn / Triton", "Pluto + Sharon"}; JList jlst = new JList(); // Declare radio buttons JRadioButton jrbMonday, jrbTuesday, jrbWednesday, jrbThursday, jrbFriday; // Create a textfield JTextField jMsg = new JTextField(10); // Create panel to hold label and textbox. JPanel p1 = new JPanel(); p1.setLayout(new BorderLayout(5,0)); p1.add(new JLabel("Name: "), BorderLayout.WEST); p1.add(new JTextField(20), BorderLayout.CENTER); jMsg.setHorizontalAlignment(JTextField.LEFT); // Create combobox panel. JPanel p2 = new JPanel(); p2.setLayout(new GridLayout(2,0,5,5)); p2.add(p1, BorderLayout.NORTH); p2.add(new JComboBox(ageRanges), BorderLayout.CENTER); p2.setBorder(new TitledBorder("Passenger Name & Age Range")); //Create listbox panel. JPanel p3 = new JPanel(); p3.setLayout(new GridLayout(1, 0)); p3.add(new JList(destination)); p3.setBorder(new TitledBorder("Destinations")); // Create a new panel to hold radio buttons. JPanel r1 = new JPanel(); r1.setLayout(new GridLayout(3,2)); r1.add(jrbMonday = new JRadioButton("Monday")); r1.add(jrbTuesday = new JRadioButton("Tuesday")); r1.add(jrbWednesday = new JRadioButton("Wednesday")); r1.add(jrbThursday = new JRadioButton("Thursday")); r1.add(jrbFriday = new JRadioButton("Friday")); r1.setBorder(new TitledBorder("Departure Days")); // Create a radio button group to group five buttons ButtonGroup group = new ButtonGroup(); group.add(jrbMonday); group.add(jrbTuesday); group.add(jrbWednesday); group.add(jrbThursday); group.add(jrbFriday); // Create grid to hold contents JPanel pMain = new JPanel(); pMain.setLayout(new BorderLayout(5,0)); add(r1, BorderLayout.CENTER); add(p2, BorderLayout.NORTH); add(p3, BorderLayout. EAST); } public static void main(String[] args) { Lab8 frame = new Lab8(); frame.pack(); frame.setTitle("Lab 8 Application"); frame.setLocationRelativeTo(null); // Center the frame frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(425, 275); frame.setVisible(true); } }
这意味着Java编译器已经注意到您的代码存在一些潜在的不安全问题,并警告您。这些问题通常非常琐碎,您可以继续进行下去。特别是因为这是学校的工作。但是要发现问题,您应该使用再次编译:javac -Xlint:unchecked Lab8.java如编译器所说。
javac -Xlint:unchecked Lab8.java
该文件中的问题是您尚未指定JComboBox和JList处理的对象的类型。由于您只处理JComboBox和JList中的字符串,因此应指定它。阅读上的Java泛型和这个以获取更多信息。
更改
String[] ageRanges = {"Under 20", "20-29", "30-39", "40-49", "50-59", "60 and Above"}; JComboBox jcbo = new JComboBox(ageRanges);
至
String[] ageRanges = {"Under 20", "20-29", "30-39", "40-49", "50-59", "60 and Above"}; JComboBox<String> jcbo = new JComboBox<String>(ageRanges);
还要更改:
p2.add(new JComboBox(ageRanges), BorderLayout.CENTER); p2.setBorder(new TitledBorder("Passenger Name & Age Range"));
p2.add(new JComboBox<String>(ageRanges), BorderLayout.CENTER); p2.setBorder(new TitledBorder("Passenger Name & Age Range"));
终于改变
//Create listbox panel. JPanel p3 = new JPanel(); p3.setLayout(new GridLayout(1, 0)); p3.add(new JList(destination));
//Create listbox panel. JPanel p3 = new JPanel(); p3.setLayout(new GridLayout(1, 0)); p3.add(new JList<String>(destination));
编辑:
不建议将其用于生产代码,但要绕过这些警告,请使用:
@SuppressWarnings("unchecked")
只需在进行不安全操作的任何方法之上添加此代码即可。例如,我认为您可以将其放在此代码中的main方法之上,如下所示:
@SuppressWarnings("unchecked") public static void main(String[] args) { ...
这样可以消除警告。