Convert Linkedlist to ArrayList

Question

I had to write a program to do LZWDecode and I decided to use LinkedList to write the LZWDecode program below but I want to convert it to an ArrayList. Anyone have idea on how I can convert the LinkedList to an ArrayList to make it simpler. Thanks.

import java.util.*;

public class LZWDecoder {

private final int CLEAR_TABLE=256;
private final int END_OF_DATA=257;
private final int TABLE_SIZE=4096;

private static LinkedList<Integer> input = new LinkedList<Integer>();
@SuppressWarnings("unchecked")
private LinkedList<Integer>[] table
        = new LinkedList[TABLE_SIZE];
private LinkedList<Integer> temp = new LinkedList<Integer>();
private int index = 258;
private LinkedList<String> trace = new LinkedList<String>();
private boolean view = true;

private void enterData() {
Scanner scan = new Scanner(System.in);
System.out.println("Please enter the Input Code (EOD = 257):");
int n=0;
while(n!=END_OF_DATA && scan.hasNextInt()){
n = scan.nextInt();
//System.out.println("Adding "+n);
input.add(n);
}

System.out.println("Decoding...\nOutput:");
String code="";
for(int i=0; i<input.size(); i++) {
code+=input.get(i)+" ";
}
trace.add("\nInput: "+code);
//test
/*
while(!input.isEmpty()) {
System.out.println(input.remove());
}
*/
}

private void reset() {
trace.add("Clearing...");
//table.clear();
for(int i=0; i<TABLE_SIZE;i++) {
table[i] = new LinkedList<Integer>();
}
}

private void decode(int c) {
switch(c) {
case CLEAR_TABLE:
trace.add("decode\t"+CLEAR_TABLE+"->[256]");
reset();
break;
case END_OF_DATA:
trace.add("decode\t"+END_OF_DATA+"->[257]");
trace.add("Decoding finished.");
break;
default:
if(c<256) {
trace.add("decode\t"+c+"->["+c+"]");
if(!temp.isEmpty()) append(c);
emit(c);
add(temp);
} else {
trace.add("decode\t"+c+"->["+printTableNode(table[c])+"]");
if(!temp.isEmpty()) append(table[c].get(0));
emit(c, table[c]);
add(temp);
}
}
}

private void emit(int n, LinkedList<Integer> c) {
//int [] a=new int[c.size()];
temp=new LinkedList<Integer>();
for(int i=0; i<c.size(); i++) {
//a[i]=c.get(i);
System.out.print(c.get(i)+" ");
temp.add(c.get(i));
}
trace.add("emit\t"+n+"->"+"["+printTableNode(c)+"]");

}

private void emit(int c) {
//print out output
temp=new LinkedList<Integer>();
temp.add(c);
trace.add("emit\t"+c+"->"+"["+c+"]");
System.out.print(c+" ");
}

/*
private void add(int c) {
//added to table is copied to temp
table[index].add(c);
temp = (LinkedList)table[index].clone();
trace.add("add\t"+index+"->["+printTableNode(table[index])+"]");
}
*/

private void add(LinkedList<Integer> c) {
for(int i=0; i<c.size();i++) {
//temp.add(c.get(i));
table[index].add(c.get(i));
}
trace.add("add\t"+index+"->["+printTableNode(table[index])+"]");
}


private void append(int c) {
//table[c].add(12);//add what?
//temp.add(c);
table[index].add(c);
trace.add("append\t"+index+"->["+printTableNode(table[index])+"]");
index++;
}

private String printTableNode(LinkedList l) {
String list="";
for(int i=0; i<l.size();i++) {
list+=l.get(i);
if(i<l.size()-1) {
list+=", ";
}
}
    return list;
}

private void printTrace() {
System.out.print("Printing Trace...");
for(int i=0; i<trace.size(); i++) {
System.out.println(trace.get(i));
}
}

public static void main(String[] args) {
// TODO code application logic here
LZWDecoder d = new LZWDecoder();
d.enterData();
while(!input.isEmpty()) {
d.decode(input.remove());
}
System.out.print("\n\n");
d.printTrace();
}

}

What do you mean with "convert"? Change it within the code or do a "cast" on it? — Tobias
– Tobias, Commented Feb 25, 2014 at 3:07
Looks like you would benefit from using an enum instead of int, then you could add behaviour to the enum and throw away your switch statements. You also wouldn't need range checking etc. See Enum vs. Int — Bohemian
– Bohemian ♦, Commented Feb 25, 2014 at 4:09

Nitin Mahesh · Accepted Answer · 2014-09-02 04:47:50Z

19

LinkedList<String> ll= new LinkedList<String>();
ll.add("A");
ll.add("B");
ll.add("C");
ll.add("D");

List<String> myAL = new ArrayList<String>(ll);

for (Object alObject : myAL)
  System.out.println(alObject);

So as you can easily convert the LinkedList to ArrayList bu using its constructor with passing Collection in it.

Hope it will clear your doubt.

answered Sep 2, 2014 at 4:47

Nitin Mahesh

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Comments

Lyju I Edwinson · Accepted Answer · 2014-02-25 03:13:30Z

5

Question is not clear enough. Do you want to use ArrayList instead of Linked List? Or do you want to convert a Linked List to an ArrayList?

First of all please declare variables on their interface not on implementation,

i.e

    LinkedList<Integer>[] table = new LinkedList[TABLE_SIZE];

Instead use

    List<Integer>[] table = new LinkedList[TABLE_SIZE];

Please provide a little more details on what you really looking for ....

If you want an array List from another collection, do this,

   List<T> t = new ArrayList<>();
   t.addAll(linkedList);

Regards Lyju

answered Feb 25, 2014 at 3:13

Lyju I Edwinson

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1 Comment

Ungeheuer Over a year ago

Why would I want to declare a LinkedList with the left hand of the assignment operator (=) being the interface List? That inherently limits functionality that I want from the LinkedList. If I did this with an ArrayList I would lose such functionality as trimToSize, etc. That seems like a pointless hobbling of functionality.

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