这里有两个类,query sentence和stackov。一个arraylist用来存储query语句类的对象,但是最近添加的对象覆盖了之前的对象,如何添加对象才不会被覆盖?
QuerySentence.java
public class QuerySentence {
public static String query;
public static String label;
public QuerySentence(){
}
public QuerySentence(String query,String label){
this.query = query;
this.label = label;
}
}
Stackov.java
package QueryClassifier;
import java.util.ArrayList;
public class stackov {
public static void main(String args[])
{
QuerySentence qs1 = new QuerySentence("What state produces the best lobster to eat","LOCATION");
QuerySentence qs2 = new QuerySentence("What is Dick Clark's birthday","DATE");
ArrayList<Object> doclist = new ArrayList<Object>();
doclist.add(0,qs1);
doclist.add(1,qs2);
int size = doclist.size();
while(size>0)
{
QuerySentence qs3 = (QuerySentence) doclist.get(size-1);
System.out.println("\nin loop : " + qs3.label + qs3.query);
size--;
}
}
}
最佳答案
问题不是来自您的循环,而是来自您的类QuerySentence
。您正在创建静态对象,这意味着您不会为类的不同实例创建不同的字段,但该类将只有它们的唯一副本。
那么这里发生了什么,您将这些值分配给您的类 QuerySentence
:
QuerySentence qs1 = new QuerySentence("What state produces the best lobster to eat","LOCATION");
然后用这个擦掉它:
QuerySentence qs2 = new QuerySentence("What is Dick Clark's birthday","DATE");
当您将两个对象添加到您的ArrayList
时,当然在您的循环中您将打印两个结果。但只有qs2中的结果。从您的字段声明中删除 static
,它将正常工作:
public String query;
public String label;
您不需要在添加时为您的查询语句编制索引。
doclist.add(qs1);
doclist.add(qs2);
而且您还可以改进循环。你可以这样做:
ArrayList<QuerySentence> doclist = new ArrayList<QuerySentence>();
// some code...
for(QuerySentence q : doclist)
{
System.out.println("In loop : " + q.label + q.query);
}
还请记住 Java 约定:您的类应以大写字母开头 (Stackov
)。如果您还致力于封装,最好将您的字段声明为 private
并为它们创建 getters
和 setters
。有了这个你的 for-statement
应该是这样的:
for(QuerySentence q : doclist)
{
System.out.println("In loop : " + q.getLabel() + q.getQuery());
}
关于java - 如何在java中将对象添加到ArrayList,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/15356889/