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    <p>For some quick references of Java complexities:</p> <ul> <li><a href="http://www.coderfriendly.com/wp-content/uploads/2009/05/java_collections_v2.pdf" rel="nofollow">http://www.coderfriendly.com/wp-content/uploads/2009/05/java_collections_v2.pdf</a></li> <li><a href="http://infotechgems.blogspot.com/2011/11/java-collections-performance-time.html" rel="nofollow">http://infotechgems.blogspot.com/2011/11/java-collections-performance-time.html</a></li> </ul> <p>But really, nothing beats looking to the source, which can be found <a href="http://hg.openjdk.java.net/jdk7/jdk7-gate/jdk/file/tip/src/share/classes/java/util/ArrayList.java" rel="nofollow">here</a>.</p> <hr> <p>Regarding the particular question of adding to an ArrayList, for example, we can see:</p> <pre><code>public boolean add(E e) { ensureCapacityInternal(size + 1); // Increments modCount!! elementData[size++] = e; return true; } </code></pre> <p>The complexity for this operation clearly depends on <em>ensureCapacityInternal</em>:</p> <pre><code>private void ensureCapacityInternal(int minCapacity) { modCount++; // overflow-conscious code if (minCapacity - elementData.length &gt; 0) grow(minCapacity); } </code></pre> <p>Which depends on <em>grow</em>:</p> <pre><code>private void grow(int minCapacity) { // overflow-conscious code int oldCapacity = elementData.length; int newCapacity = oldCapacity + (oldCapacity &gt;&gt; 1); if (newCapacity - minCapacity &lt; 0) newCapacity = minCapacity; if (newCapacity - MAX_ARRAY_SIZE &gt; 0) newCapacity = hugeCapacity(minCapacity); // minCapacity is usually close to size, so this is a win: elementData = Arrays.copyOf(elementData, newCapacity); } </code></pre> <p>So we can see that the grow operation happens conditionally, and that in many cases, adding will be an O(1) operation. But you can also see from this the details of <em>when</em> the array will grow.</p>
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    1. POWhat is the runtime of operations on Java's Arraylist?
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    1. POWhat is the runtime of operations on Java's Arraylist?
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    1. COThat's not very helpful - it doesn't cover the complexities of collection complexity. For example that a `LinkedList` never has to expand to so `add` always takes the same constant time whereas for an `ArrayList` there sometimes needs to be a `System.arraycopy` call.
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    2. COYes, like I said, it's good to have an understanding of how the collection implementation works. Still, I feel that such a reference is helpful, because it is somewhat analogous to the example list the OP provided for Python list.
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    3. COTo allow for understanding of what actually happens for the different ArrayList operations, I've provided a link to ArrayList source.
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