Here’s a good way to create a true memory leak (objects inaccessible by running code but still stored in memory) in pure Java: The application creates a long-running thread (or use a thread pool to leak even faster). The thread loads a class via an (optionally custom) ClassLoader. The class allocates a large chunk of … Read more
If you’re only interested in the keys, you can iterate through the keySet() of the map: Map<String, Object> map = …; for (String key : map.keySet()) { // … } If you only need the values, use values(): for (Object value : map.values()) { // … } Finally, if you want both the key and … Read more
Strings are immutable. That means once you’ve created the String, if another process can dump memory, there’s no way (aside from reflection) you can get rid of the data before garbage collection kicks in. With an array, you can explicitly wipe the data after you’re done with it. You can overwrite the array with anything … Read more
As always with these questions, the JLS holds the answer. In this case §15.26.2 Compound Assignment Operators. An extract: A compound assignment expression of the form E1 op= E2 is equivalent to E1 = (T)((E1) op (E2)), where T is the type of E1, except that E1 is evaluated only once. An example cited from §15.26.2 […] the following code is … Read more
Map<String, String> map = … for (Map.Entry<String, String> entry : map.entrySet()) { System.out.println(entry.getKey() + “/” + entry.getValue()); } On Java 10+: for (var entry : map.entrySet()) { System.out.println(entry.getKey() + “/” + entry.getValue()); }
Android R Update: From Android R, this method always returns false. Google says that this is done “to protect goat privacy”: /** * Used to determine whether the user making this call is subject to * teleportations. * * <p>As of {@link android.os.Build.VERSION_CODES#LOLLIPOP}, this method can * now automatically identify goats using advanced goat recognition … Read more
In Java 1.7 or later, the standard way to do this is as follows: import java.util.concurrent.ThreadLocalRandom; // nextInt is normally exclusive of the top value, // so add 1 to make it inclusive int randomNum = ThreadLocalRandom.current().nextInt(min, max + 1); See the relevant JavaDoc. This approach has the advantage of not needing to explicitly initialize … Read more