Comparing the time to convert a List to an Array versus remaining as an Array.

listToArray.java

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


public class TestListToArrayConversion {

	public static void main(String[] args) {
		Map<String, Object> testMap = new HashMap<String, Object>();
		
		List<TestString> testStrs = new ArrayList<TestString>();
		for(int i = 0; i < 10; i++) {
			testStrs.add(new TestString());
		}
		
		long startTime = System.nanoTime();
		for(long i = 0; i < 100000000; i++) {
			testMap.put("TestArray", getTestArray(testStrs));
		}
		
		System.out.println("Array: " + (System.nanoTime() - startTime));
		startTime = System.nanoTime();
		
		for(long i = 0; i < 100000000; i++) {
			testMap.put("TestList", getTestList(testStrs));
		}
		System.out.println("List:  " + (System.nanoTime() - startTime));
	}
	
	private static List<String> getTestList(List<TestString> strings) {
		List<String> testList = new ArrayList<String>();
		for(TestString testStr : strings) {
			testList.add(testStr.getString());
		}
		return testList;
	}
	
	private static String[] getTestArray(List<TestString> strings) {
		List<String> testList = new ArrayList<String>();
		for(TestString testStr : strings) {
			testList.add(testStr.getString());
		}
		return testList.toArray(new String[testList.size()]);
	}
	
	private static class TestString {
		
		private final String str;
		
		public TestString() {
			this.str = "test";
		}
		
		public String getString() {
			return str;
		}
		
	}
	
}


/**
* Array: 14384976374
* List:  10540872310
*/