|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 |
// In Java another constructor of the same class can be called // from a constructor using 'this()'. // Note: 'this()' has to be on the first line. public class Foo { private int x; public Foo() { this(1); } public Foo(int x) { this.x = x; } } |
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 |
import java.util.Arrays; /** * Algorithm * * 1] Compare each pair of adjacent elements from beginning * of an array and, if they are in reversed order, swap them. * * 2] If at least one swap has been done, repeat step 1. * */ public class MyBubbleSort { private void sortData(int[] data) { boolean swapDone = false; do { swapDone = false; for (int i = 0; i < data.length-1; i++) { if (data[i] > data[i+1]) { swapDone = true; int tmp = data[i]; data[i] = data[i+1]; data[i+1] = tmp; } } } while (swapDone == true); } public static void main(String[] args) { int[] data = {5,1,12,-5,16}; System.out.println(Arrays.toString(data)); new MyBubbleSort().sortData(data); System.out.println(Arrays.toString(data)); } } |
HashMap is a non-synchronized collection class. If we need to perform thread-safe operations on it then we must need to synchronize it explicitly.
Iterator should be used in a synchronized block even if we have synchronized the HashMap explicitly.
|
1 2 3 4 5 6 7 8 9 10 11 12 |
Map map = Collections.synchronizedMap(new HashMap()); ... // This doesn't need to be in synchronized block Set set = map.keySet(); // Synchronizing on map, not on set synchronized (map) { // Iterator must be in synchronized block Iterator iterator = set.iterator(); while (iterator.hasNext()) { ... } } |