.java使用未經檢查和不安全的操作

Question

這是我的Java代碼：

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();
    }
}

這段代碼給我警告。java使用未經檢查和不安全的操作。 我有考試，所以請幫助我進行考試 。

Answer 1

您應該為JList使用類型參數，因為這是一個泛型錯誤，並且JList支持泛型。

更改：

JList list到JList<String> list
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);
    }    
}

有關此主題的信息和示例，請參見課程：泛型 。