好的，所以我对java非常新。我正在努力为一堂课完成作业但是我被卡住了。我一直在主要的数组列表中收到错误，所以它不会运行，也不知道为什么或如何解决它。错误说“语法错误，参数化类型仅在源级别为5.0时可用”和“类型ArrayList不是通用的;它不能使用参数进行参数化”。我班上的某个人已经建议改变一些名为“合规”的东西，但是后来它开始说我的代码中没有主要内容，即使有明确的内容。我在学校的Citrix服务器上使用Eclipse。希望你们能帮助我解决问题，以便我可以运行代码。请帮我。该网站不会让我发布错误的屏幕截图，但它是在这些行....
ArrayList<Double>priceList = new ArrayList<Double>();
ArrayList<Double> quantityList = new ArrayList<Double>();
ArrayList<Double> amountList = new ArrayList<Double>();
这是节目描述.....
编写一个名为ThreeArrayLists.java的程序，该程序声明由名为priceList，quantityList和amountList的对象引用的三个ArrayList对象。每个ArrayList都应该在main（）中声明，并且应该能够保存至少10个双精度数。 应存储在priceList中的数字是10.62,14.89,13.21,16.55,18.62,9.47,6.58,18.32,12.15,3.98。 应存储在quantityList中的数字是4,8.5,6,7.35,9,15.3,3,4.4,2.9 4.8。 您的程序应该将对这三个ArrayList对象的对象引用传递给名为extend（）的方法，该方法应该将amountListArrayList中的元素计算为priceList和quantityListArrayList中相应元素的乘积，例如amountList.add（priceList.get） （i）* quantityList.get（i））。 Afterextend（）已将值放入amountListArrayList对象中，创建一个显示所有三个列表结果的方法。需要使用适当的格式化技术来生成格式化的输出。
...以下是完整的代码。
package week6;
import java.text.DecimalFormat;
import java.util.ArrayList;
public class ThreeArrayLists extends javax.swing.JFrame {
static String result;
public ThreeArrayLists() {
initComponents();
}
private void initComponents() {
jLabel1 = new javax.swing.JLabel();
jLabel2 = new javax.swing.JLabel();
ProceTextField = new javax.swing.JTextField();
jLabel3 = new javax.swing.JLabel();
QuantityTextField = new javax.swing.JTextField();
CalculateButton = new javax.swing.JButton();
jLabel4 = new javax.swing.JLabel();
jScrollPane1 = new javax.swing.JScrollPane();
ResultTextArea = new javax.swing.JTextArea();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
setTitle("ThreeArrayLists");
jLabel1.setFont(new java.awt.Font("Tahoma", 1, 14));
jLabel1.setText("ThreeArrayLists");
jLabel2.setFont(new java.awt.Font("Tahoma", 1, 12));
jLabel2.setText("priceList:");
ProceTextField.setEditable(false);
ProceTextField.setText("{ 10.62, 14.89, 13.21, 16.55, 18.62, 9.47, 6.58, 18.32, 12.15, 3.98 }");
jLabel3.setFont(new java.awt.Font("Tahoma", 1, 12));
jLabel3.setText("quantityList:");
QuantityTextField.setEditable(false);
QuantityTextField.setText("{ 10.62, 14.89, 13.21, 16.55, 18.62, 9.47, 6.58, 18.32, 12.15, 3.98 }");
CalculateButton.setText("Calculate");
CalculateButton.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
CalculateButtonActionPerformed(evt);
}
});
jLabel4.setFont(new java.awt.Font("Tahoma", 1, 12));
jLabel4.setText("amountList:");
ResultTextArea.setColumns(20);
ResultTextArea.setRows(5);
jScrollPane1.setViewportView(ResultTextArea);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(26, 26, 26)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(78, 78, 78)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 361, Short.MAX_VALUE)
.addGroup(layout.createSequentialGroup()
.addComponent(jLabel4)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 287, Short.MAX_VALUE))))
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jLabel3)
.addComponent(jLabel2, javax.swing.GroupLayout.PREFERRED_SIZE, 65, javax.swing.GroupLayout.PREFERRED_SIZE))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(QuantityTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(ProceTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 9, Short.MAX_VALUE)))
.addGap(46, 46, 46))
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addContainerGap(235, Short.MAX_VALUE)
.addComponent(CalculateButton)
.addGap(199, 199, 199))
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addContainerGap(208, Short.MAX_VALUE)
.addComponent(jLabel1)
.addGap(194, 194, 194))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jLabel1)
.addGap(26, 26, 26)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel2)
.addComponent(ProceTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(30, 30, 30)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel3)
.addComponent(QuantityTextField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(32, 32, 32)
.addComponent(CalculateButton)
.addGap(21, 21, 21)
.addComponent(jLabel4)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 195, Short.MAX_VALUE)
.addContainerGap())
);
pack();
}
private void CalculateButtonActionPerformed(java.awt.event.ActionEvent evt) {
ResultTextArea.setText(result);
}
public static void main(String args[]) {
DecimalFormat df = new DecimalFormat("###,###.00");
double[] PRICE_ARRAY = { 10.62, 14.89, 13.21, 16.55, 18.62, 9.47, 6.58, 18.32, 12.15, 3.98 };
double[] QUANTITY_ARRAY = { 4.0, 8.5, 6.0, 7.35, 9.0, 15.3, 3.0, 5.4, 2.9, 4.8 };
ArrayList<Double>priceList = new ArrayList<Double>();
ArrayList<Double> quantityList = new ArrayList<Double>();
ArrayList<Double> amountList = new ArrayList<Double>();
for (int i=0; i < 10; i++){
priceList.add(new Double(PRICE_ARRAY[i]));
quantityList.add(new Double(QUANTITY_ARRAY[i]));
}
result = "";
for (int i = 0; i < 10; i++) {
amountList.add((Double.valueOf(priceList.get(i).toString())) * (Double.valueOf(quantityList.get(i).toString())));
result += String.valueOf(i+1) + ") "
+ new String(df.format(priceList.get(i))) + " * "
+ new String(df.format(quantityList.get(i))) + " = "
+ new String(df.format(amountList.get(i))) + "\n";
}
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new ThreeArrayLists().setVisible(true);
}
});
}
private javax.swing.JButton CalculateButton;
private javax.swing.JTextField ProceTextField;
private javax.swing.JTextField QuantityTextField;
private javax.swing.JTextArea ResultTextArea;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JLabel jLabel4;
private javax.swing.JScrollPane jScrollPane1;
}
答案 0 :(得分：1)
在我看来，您使用的JDK可能低于1.5版本，在Java 5之前不会引入泛型。
您可以尝试声明您的列表：
ArrayList priceList = new ArrayList();
然后，如果您想稍后操作数据，则需要记住在引用元素时强制转换为Double。
答案 1 :(得分：0)
Java 不处理泛型类型（也称为其他类型参数化的类型：List）。
要在 Java 1.4中运行代码，您需要松开泛型类型参数并自行执行转换。贝娄是一种如何实现类似于你的目标的方式。
示例：
import java.util.ArrayList;
public class test {
String result;
double[] PRICE_ARRAY = { 10.62, 14.89, 13.21, 16.55, 18.62, 9.47, 6.58, 18.32, 12.15, 3.98 };
double[] QUANTITY_ARRAY = { 4.0, 8.5, 6.0, 7.35, 9.0, 15.3, 3.0, 5.4, 2.9, 4.8 };
ArrayList priceList = new ArrayList();
ArrayList quantityList = new ArrayList();
ArrayList amountList = new ArrayList();
public void homework(){
for (int i=0; i < 10; i++){
this.priceList.add((Double)(PRICE_ARRAY[i]));
this.quantityList.add((Double)(QUANTITY_ARRAY[i]));
this.amountList.add((Double)priceList.get(i) * (Double)quantityList.get(i));
}
}
public void output(){
System.out.println("Price list: " + priceList.toString());
System.out.println("Quantity list: " + quantityList.toString());
System.out.println("Amount list: " + amountList.toString());
}
}