求大佬看下！！！！！！！！！！！

[Lin_bai_]

定义泛型类（Miami<T>）在创建两个类（Detroit和Philadelphia）继承该泛型类
这个应该怎么写呀大佬
class Miami<T>
{
class Detroit;
public Miami(String Detroit)
{
this.Detroit = Detroit;
}
class Philadelphia;
public Miami( String Philadelphia)
{
this.Philadelphia = Philadelphia;
}
}
求大佬解答

[Lin_bai_]

这个应该怎么写？？？？

[Lin_bai_]

package GenericProgramma; class Miami<T> { private T[] Detroit; private T[] Philadelphia; public Miami(T[] Detroit,T[] Philadelphia) { this.Detroit = Detroit; this.Philadelphia = Philadelphia; } public Miami(String[] info) { } public void showBookInfo() { System.out.println("银行名称\t\t存款时间\t户名\t币种\t存款金额\t账户余额"); for (int i = 0;i < Detroit.length;i++) { System.out.print(Detroit[i]+"\t"); } } public void showBookInfo1() { System.out.println("银行名称\t\t存款时间\t户名\t币种\t存款金额\t账户余额"); for (int i = 0;i<Philadelphia.length;i++) { System.out.print(Philadelphia[i]+"\t"); } } public static void main(String[] args) { String[] info = {"张三","Rmb","8888.00RMB","18,888.88RMB"}; String[] info1 = {"张三","Rmb","8888.00RMB","18,888.88RMB"}; Miami<String> bank = new Miami<String>(info); Miami<String> bank1 = new Miami<String>(info1); bank.showBookInfo(); bank1.showBookInfo1(); } } 这是我之后写的，报错了 银行名称 存款时间 户名 币种 存款金额 账户余额 Exception in thread "main" java.lang.NullPointerException at GenericProgramma.Miami.showBookInfo(Arbitrarily.java:21) at GenericProgramma.Miami.main(Arbitrarily.java:40) 提示这个 是什么原因呀

[fengchuiqi_]

首先Miami<String> bank = new Miami<String>(info); 这个只是new了一个对象。构造方法也没有赋值，所以你的bank是null，然后调用方法for循环的时候回报空指针，那是因为Detroit.length=0。你这个代码写的太乱了。我按照题意写了一下

class Miami<T> {

    private String name;//银行名称
    private String time;//存款时间
    private String user;//户名
    private String type;//币种
    private String money;//存款金额
    private String balance;//账户余额

    public void setName(String name) {
        this.name = name;
    }

    public void setTime(String time) {
        this.time = time;
    }

    public void setUser(String user) {
        this.user = user;
    }

    public void setType(String type) {
        this.type = type;
    }

    public void setMoney(String money) {
        this.money = money;
    }

    public void setBalance(String balance) {
        this.balance = balance;
    }

    public Miami(String name, String time, String user, String type, String money, String balance) {
        this.name = name;
        this.time = time;
        this.user = user;
        this.type = type;
        this.money = money;
        this.balance = balance;
    }

    public Miami() {
    }

    public String showBookInfo(){
       return "银行名称:"+name+"\t存款时间:"+time+"\t户名:"+user+"\t币种:"+type+"\t存款金额:"+money+"\t账户余额:"+balance;
    }


    class Detroit extends Miami<String> {
        public Detroit(String name, String time, String user, String type, String money, String balance) {
            super(name, time, user, type, money, balance);
        }
        @Override
        public String showBookInfo() {
            return super.showBookInfo();
        }
    }

    class Philadelphia extends Miami<String> {

        public Philadelphia(String name, String time, String user, String type, String money, String balance) {
            super(name, time, user, type, money, balance);
        }
        @Override
        public String showBookInfo() {
            return super.showBookInfo();
        }
    }

    public static void main(String[] args) {
        Miami m1 = new com.Test1.Detroit("中国银行","1999-1-1","二狗","人名币","10000000.00","20000.00");
        Miami m2 = new com.Test1.Philadelphia("农行","1999-1-31","二狗","人名币","10000000.00","20000.00");
        System.out.println(m1.showBookInfo());
        System.out.println(m2.showBookInfo());
    }

}

结果如下

[fengchuiqi_]

引用 2 楼 Lin_bai_ 的回复:

顺便问一下，你是用的什么编译工具？直接拿class开头，然后又在类里边写类这样编译不难受吗？

[Lin_bai_]

引用 4 楼 fengchuiqi_ 的回复:

引用 2 楼 Lin_bai_ 的回复:

顺便问一下，你是用的什么编译工具？直接拿class开头，然后又在类里边写类这样编译不难受吗？

idea