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For some pointers on how to benchmark Java code, see How do I write a correct micro-benchmark in Java?

For some pointers on how to benchmark Java code, see How do I write a correct micro-benchmark in Java?

default list: 74ms
pre-sized list: 53ms
array: 41ms

public class Clazz {
    
    static final int N = 1000000;
    
    interface Test {
        void test();
    }
    static final class DfltListTest implements Test {
        public void test() {
            for (int j = 0; j < 10; ++j) {
                List<Integer> list = new ArrayList<Integer>();
                for (int i = 0; i < N; ++i) {
                    list.add(i);
                }
            }
        }
    }
    static final class SizedListTest implements Test {
        public void test() {
            for (int j = 0; j < 10; ++j) {
                List<Integer> list = new ArrayList<Integer>(N);
                for (int i = 0; i < N; ++i) {
                    list.add(i);
                }
            }
        }
    }
    static final class ArrayTest implements Test {
        public void test() {
            for (int j = 0; j < 10; ++j) {
                Integer[] arr = new Integer[N];
                for (int i = 0; i < N; ++i) {
                    arr[i] = i;
                }
            }
        }
    }
    
    static void test(Test t, String name) {
        final int iter = 11;
        final long timings[] = new long[iter];
        for (int k = 0; k < iter; ++k) {
            long t1 = System.currentTimeMillis();
            t.test();
            long t2 = System.currentTimeMillis();
            timings[k] = t2 - t1;
            System.gc();
        }
        Arrays.sort(timings);
        System.out.printf("%s: %dms\n", name, timings[iter / 2]);
    }

    public static void main(String[] args) {
        for (int i = 0; i < 5; ++i) {
            test(new DfltListTest(), "default list");
            test(new SizedListTest(), "pre-sized list");
            test(new ArrayTest(), "array");
        }
    }
}

default list: 74ms
pre-sized list: 54ms
Integer array: 42ms
int array: 9ms

public class Clazz {
    
    static final int N = 1000000;
    
    interface Test {
        void test();
    }
    static final class DfltListTest implements Test {
        public void test() {
            for (int j = 0; j < 10; ++j) {
                List<Integer> list = new ArrayList<Integer>();
                for (int i = 0; i < N; ++i) {
                    list.add(i);
                }
            }
        }
    }
    static final class SizedListTest implements Test {
        public void test() {
            for (int j = 0; j < 10; ++j) {
                List<Integer> list = new ArrayList<Integer>(N);
                for (int i = 0; i < N; ++i) {
                    list.add(i);
                }
            }
        }
    }
    static final class IntegerArrayTest implements Test {
        public void test() {
            for (int j = 0; j < 10; ++j) {
                Integer[] arr = new Integer[N];
                for (int i = 0; i < N; ++i) {
                    arr[i] = i;
                }
            }
        }
    }
    static final class IntArrayTest implements Test {
        public void test() {
            for (int j = 0; j < 10; ++j) {
                int[] arr = new int[N];
                for (int i = 0; i < N; ++i) {
                    arr[i] = i;
                }
            }
        }
    }
    
    static void test(Test t, String name) {
        final int iter = 11;
        final long timings[] = new long[iter];
        for (int k = 0; k < iter; ++k) {
            long t1 = System.currentTimeMillis();
            t.test();
            long t2 = System.currentTimeMillis();
            timings[k] = t2 - t1;
            System.gc();
        }
        Arrays.sort(timings);
        System.out.printf("%s: %dms\n", name, timings[iter / 2]);
    }

    public static void main(String[] args) {
        for (int i = 0; i < 5; ++i) {
            test(new DfltListTest(), "default list");
            test(new SizedListTest(), "pre-sized list");
            test(new IntegerArrayTest(), "Integer array");
            test(new IntArrayTest(), "int array");
        }
    }
}

(Note that these are in units of milliseconds and not tens of milliseconds used in your code/question.)

I've tested it using Java 1.7.0_09 with -XX:+AggressiveOpts -XX:CompileThreshold=1.

Note that these are in units of milliseconds. Your code performs measurements in tens of milliseconds: (t2-t1)/10.0.

I've tested it using Java 1.7.0_09 with -XX:+AggressiveOpts -XX:CompileThreshold=1.

When I tested the same code using Java 6, the ranking was the same, but the difference between default list and pre-sized list was much more significant. I've not attempted to understand what it is about Java 7 that makes the difference so much smaller.