This is an example of how to make a safe List copy. Making a safe List copy implies that you should:
- Create a new synchronized ArrayList, using the
synchronizedList(List list)API method of Collections. - Add elements to the list, using
add(Object e)API method of List. - Create a new array from the list, using
toArray(T[] a)API method of List. - An other way is to put the list in a
synchronizedstatement and again put the list elements in a new array. - Print all elements of the array, using the
output(String[] word)method of the example.
Let’s take a look at the code snippet that follows:
package com.javacodegeeks.snippets.core;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class SafeListCopy extends Object {
public static void output(String[] word) {
System.out.println("characters=" + word.length);
for (int i = 0; i < word.length; i++) {
System.out.println("word[" + i + "]=" + word[i]);
}
}
public static void main(String[] args) {
List wordList = Collections.synchronizedList(new ArrayList());
wordList.add("JavaCodeGeeks");
wordList.add("is");
wordList.add("cool!");
String[] aword = (String[]) wordList.toArray(new String[0]);
output(aword);
String[] bword;
synchronized (wordList) {
int size = wordList.size();
bword = new String[size];
wordList.toArray(bword);
}
output(bword);
String[] cword;
synchronized (wordList) {
cword = (String[]) wordList.toArray(new String[wordList.size()]);
}
output(cword);
}
}
Output:
characters=3
word[0]=JavaCodeGeeks
word[1]=is
word[2]=cool!
characters=3
word[0]=JavaCodeGeeks
word[1]=is
word[2]=cool!
characters=3
word[0]=JavaCodeGeeks
word[1]=is
word[2]=cool!
This was an example of how to make a safe List copy in Java.
