[英].java uses unchecked and unsafe operation
here is my java code: 这是我的Java代码:
import javax.swing.*;
public class Employee1 extends JFrame {
JPanel panel;
JLabel l1;
JList list;
public Employee1() {
super("Employee Details");
panel = new JPanel();
l1 = new JLabel("City : ");
String cities[] = {"Mumbai", "Delhi", "Madras"};
list = new JList(cities);
panel.add(l1);
panel.add(list);
getContentPane().add(panel);
setSize(400, 400);
setVisible(true);
}
public static void main(String args[]) {
Employee1 obj = new Employee1();
}
}
this code gives me warning .java uses unchecked and unsafe operation. 这段代码给我警告。java使用未经检查和不安全的操作。 i have exams so please help me to go through it .
我有考试,所以请帮助我进行考试 。
You should make use of a type parameter for your JList because this is a generics error and JList supports genercis. 您应该为JList使用类型参数,因为这是一个泛型错误,并且JList支持泛型。
Change: 更改:
JList list
to JList<String> list
JList list
到JList<String> list
and list = new JList(cities)
to list = new JList<>(cities)
和
list = new JList(cities)
到list = new JList<>(cities)
public class Employee1 extends JFrame {
private final JPanel panel;
private final JLabel l1;
private final JList<String> list; // <--- first change
public Employee1() {
super("Employee Details");
final String[] cities = {"Mumbai", "Delhi", "Madras"};
panel = new JPanel();
l1 = new JLabel("City : ");
list = new JList<>(cities); // <--- second change
panel.add(l1);
panel.add(list);
getContentPane().add(panel);
setSize(400, 400);
setVisible(true);
}
}
See Lesson: Generics for information and examples on this topic 有关此主题的信息和示例,请参见课程:泛型 。
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