为什么用Java中的addLast（）替换我的链表？

Question

I have a class that is supposed to create a hash table with a linked list for the values. If the key is new, it creates a linked list, and if it already exists it is supposed to append it to the end of the list. For some reason, when I use addLast() it is replacing the contents of my list. Can you see what I am doing wrong? Here is my code. Thank you!

import java.util.*;

public class Semantic {
    String currentScope;
    Stack theStack = new Stack();
    HashMap<String, LinkedList> SymbolTable= new HashMap<String, LinkedList>();


    public boolean insertSymbol(String key, SymbolTableItem value){
        LinkedList<SymbolTableItem> temp = new LinkedList<SymbolTableItem>();
        SymbolTableItem obj;
        if(!isContained(SymbolTable.get(key), value)){
            if(SymbolTable.get(key) != null){
                temp = SymbolTable.get(key);
            }
            temp.addLast(value);
            SymbolTable.put(key, temp);
            return true;
        }
        return false;
    }

    public boolean isContained(LinkedList list, SymbolTableItem obj){
        if(list == null) return false;
        while(!list.isEmpty()){
            SymbolTableItem item;
            item = (SymbolTableItem) list.removeFirst();
            if(item.equals(obj))
                return true;
        }
        return false;
    }

    public String printValues(){
        return SymbolTable.toString();
    }

    public boolean isBoolean(){
        return true;
    }

    public boolean isTypeMatching(){
        return true;
    }

    public void stackPush(String theString){
        theStack.add(theString);
    }

}

Answer 1

The method isContained removes every element up to and including the search element SymbolTableItem obj .

If obj occurs last in the LinkedList then everything will be removed.

Answer 2

Check around item = (SymbolTableItem) list.removeFirst();
The isContained method looks messed up.

Answer 3

It looks like you're creating a new linked list before you test whether the value is new or not. Try not creating the linked list until after you've tried to retrieve that value.