尝试向预定义列表对象添加新列表对象时出错

Question

我正在使用Java8开发Spring Boot Version2，当我试图在“createTopic”方法中将一个新的列表对象添加到预定义的列表对象（即topicList）中时，我得到了一个错误。

**

TopicService.java

**

public class TopicService {

    private List<TopicObject>  topicList = Arrays.asList(
            new TopicObject("Java", "Java Course", "Spring boot in java"),
            new TopicObject("Maths", "Mathematics class","12th maths")
    );



    public String createTopic(TopicObject topicObj){

         topicList.add(new TopicObject("Java1", "Java Course1", "Spring boot in java1"));

        return "Request successful"  ;
    }
}

**

package io.javabrains.springBootStarter.controller;

import com.fasterxml.jackson.annotation.JsonProperty;

public class TopicObject {

    @JsonProperty("id")
    private String id;

    @JsonProperty("name")
    private String name;

    @JsonProperty("description")
    private String description;

    public TopicObject() {
    }

    public TopicObject(String id, String name, String description) {
        this.id = id;
        this.name = name;
        this.description = description;
    }


    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

}

2020-04-15 19:52:27.172错误15312---[nio-8080-exec-2]O.A.C.C.C.[.[.[/].[dispatcherServlet]:路径为[]的上下文中servlet[dispatcherServlet]的servlet.service（）引发异常[请求处理失败；嵌套异常为java.lang.UnsupportedOperationException]并具有根本原因

>不知道是否可以通过这种方式将一个新对象添加到“topiclist”中。有人能帮忙吗？

Answer 1

arrays.aslit重新运行不可修改的list对象。如果要向其中添加元素，则需要使用可修改的list类型，例如arraylist:

private List<TopicObject>  topicList = new ArrayList<>(Arrays.asList(
        new TopicObject("Java", "Java Course", "Spring boot in java"),
        new TopicObject("Maths", "Mathematics class", "12th maths")
));