To track the order of insertion, you can use Map.Entry() in case of a Map. Let’s say we have the following LinkedHashMap −Mapmap = new LinkedHashMap(); map.put("Jack", 0); map.put("Tim", 1); map.put("David", 2); map.put("Tom", 3); map.put("Kevin", 4); map.put("Jeff", 5);Now, loop through Map.Entry and get the order of insertion correctly with Key and Value −for (Map.Entryentry: map.entrySet()) {    System.out.println(entry.getKey() + " => " + entry.getValue()); }Example Live Demoimport java.util.LinkedHashMap; import java.util.Map; public class Demo {    public static void main(String[] args) {       Mapmap = new LinkedHashMap();       map.put("Jack", 0);       map.put("Tim", 1);       ... Read More

Let’s say the following is our HashMap −HashMapmap = new HashMap(); map.put(10, "A"); map.put(20, "B"); map.put(30, "C"); map.put(40, "D"); map.put(50, "E"); map.put(60, "F"); map.put(70, "G"); map.put(80, "H");To retrieve all the keys, iterator through each and every key-value pair −Setset = map.keySet(); Iteratori = set.iterator(); while (i.hasNext()) {    Integer res = i.next();    System.out.println(res + ": " + map.get(res)); }Example Live Demoimport java.util.HashMap; import java.util.Iterator; import java.util.Set; public class Demo {    public static void main(String[] args) {       HashMapmap = new HashMap();       map.put(10, "A");       map.put(20, "B");       map.put(30, "C");   ... Read More

In Java, the HashMap class is a part of the Java.util package and provides a convenient way to store key-value pairs. Sometimes, We need to update the values of existing keys while keeping the keys identical. This can be easily achieved using the put() method, replace() method, and computeIfPresent() method which allows to replace the value with a specific key. Creating a HashMap and setting key-value pair − Mapmap = new HashMap(); map.put(10, "A"); map.put(20, "B"); map.put(30, "C"); Now, let's set a different value for an identical key using the put(), replace(), and computeIfPresent() methods − map.put(10, "T"); map.replace(10, "T"); map.computeIfPresent(10, ... Read More

Let us first crate OutputStream with file input.txt −FileOutputStream fileStream = new FileOutputStream("E:/input.txt"); DataOutputStream dataStream = new DataOutputStream(fileStream);Now, the writeBytes() method writes out the string to the underlying output stream as a sequence of bytes.dataStream.writeBytes("Demo text!");Flush the output stream −dataStream.flush();The following is an example. Here, our file is “E:/input.txt” and at the end we are flushing the output stream −Exampleimport java.io.DataOutputStream; import java.io.FileOutputStream; public class Demo {    public static void main(String[] args) throws Exception {       FileOutputStream fileStream = new FileOutputStream("E:/input.txt");       DataOutputStream dataStream = new DataOutputStream(fileStream);       dataStream.writeBytes("Demo text!");       ... Read More

Let’s say the following is our HashMap −HashMapmap = new HashMap();Add key value pair to the HashMap −map.put("1", "A"); map.put("2", "B"); map.put("3", "C"); map.put("4", "D"); map.put("5", "E"); map.put("6", "F"); map.put("7", "G"); map.put("8", "H"); map.put("9", "I");Now, use the remove() method to remove the key-value pair −map.remove("5");Example Live Demoimport java.util.Collection; import java.util.HashMap; import java.util.Iterator; import java.util.LinkedHashMap; import java.util.Map; import java.util.Set; public class Demo {    public static void main(String[] args) {       HashMapmap = new HashMap();       map.put("1", "A");       map.put("2", "B");       map.put("3", "C");       map.put("4", "D");       map.put("5", "E"); ... Read More

Let’s say the value you have set is 20 and you have to display a prime number less than this value i.e. 19 in this case.The following is an example that displays a prime number less than the given number −Example Live Demopublic class Demo {    public static void main(String[] args) {       int val = 20;       boolean[] isprime = new boolean[val + 1];       for (int i = 0; i

To convert positive int to negative and vice-versa, use the Bitwise Complement Operator.Let us first initialize a positive int −int positiveVal = 200;Now, let us convert it to negative −int negativeVal = (~(positiveVal - 1));Now, let’s say we have the following negative int −int negativeVal = -300;The following will convert the negative to positive int −positiveVal = ~(negativeVal - 1);Example Live Demopublic class Demo {    public static void main(String[] args) throws java.lang.Exception {       int positiveVal = 100;       int negativeVal = (~(positiveVal - 1));       System.out.println("Result: Positive value converted to Negative = "+negativeVal); ... Read More

The java.math.BigDecimal.movePointRight(int n) returns a BigDecimal which is equivalent to this one with the decimal point moved n places to the right. If n is non-negative, the call merely subtracts n from the scale.The java.math.BigDecimal.scaleByPowerOfTen(int n) returns a BigDecimal whose numerical value is equal to (this * 10n). The scale of the result is (this.scale() - n).The following is an example displaying the usage of both −Example Live Demoimport java.math.BigDecimal; public class Demo {    public static void main(String... args) {       long base = 3676;       int scale = 5;       BigDecimal d = ... Read More

To read the Map, first use getProperties() ad then iterator to iterate through the entire list of Map −Properties prop = System.getProperties(); Iterator i = prop.entrySet().iterator();Now, loop through Map.Entry and get the key-value pair for the Map −while (i.hasNext()) {    Map.Entry entry = (Map.Entry) i.next();    System.out.println(entry.getKey() + " => " + entry.getValue()); }Example Live Demoimport java.util.Iterator; import java.util.Map; import java.util.Properties; public class Demo {    public static void main(String[] a) {       Properties prop = System.getProperties();       Iterator i = prop.entrySet().iterator();       while (i.hasNext()) {          Map.Entry entry = (Map.Entry) ... Read More

Create a Map and insert elements to in the form of key and value −HashMap map = new HashMap (); map.put("1", "A"); map.put("2", "B"); map.put("3", "C"); map.put("4", "D"); map.put("5", "E"); map.put("6", "F"); map.put("7", "G"); map.put("8", "H"); map.put("9", "I");Now, loop through Map by Map.Entry. Here, we have displayed the key and value separately −Sets = map.entrySet(); Iteratori = s.iterator(); while (i.hasNext()) {    Map.Entrye = (Map.Entry) i.next();    String key = (String) e.getKey();    String value = (String) e.getValue();    System.out.println("Key = "+key + " => Value = "+ value); }Example Live Demoimport java.util.HashMap; import java.util.Iterator; import java.util.LinkedHashMap; import java.util.Map; ... Read More