import java.util.ArrayList; import java.util.Arrays; import java.util.List; import java.util.function.Function; public class Demo { public static void main(String args[]) { List < Employee > emp = Arrays.asList(new Employee("Jack", 29, "South"), new Employee("Tom", 24, "North"), new Employee("Harry", 35, "West"), new Employee("Katie", 32, "East")); List < String > res = processElements(emp, p -> p.displayEmpName()); System.out.println("Employee Names + " + res); } public static < X, Y > List < Y > processElements(Iterable < X > src, Function < X, Y > mapper) { List < Y > list = new ArrayList <> (); for (X p: src) list.add(mapper.apply(p)); return list; } } class Employee { private String emp_name; private int emp_age; private String emp_zone; public Employee(String emp_name, int emp_age, String emp_zone) { this.emp_name = emp_name; this.emp_age = emp_age; this.emp_zone = emp_zone; } public String displayEmpName() { return this.emp_name; } }
import java.util.*; public class Demo { public static void main(String[] s) { Hashtable<String,String>hash = new Hashtable<String,String>(); hash.put("key1", "value1"); hash.put("key2", "value2"); hash.put("key3", "value3"); System.out.println("Initial collection: "+hash); Map map= Collections.unmodifiableMap(hash); // error will generate map.put("key3", "value3"); } }
import java.util.ArrayList; import java.util.Collections; import java.util.LinkedList; import java.util.List; import java.util.ListIterator; public class Demo { public static void main(String[] args) { String[] str = { "P", "Q", "R", "S", "T", "U", "V", "W" }; int len = str.length; List<String>list1 = new ArrayList<String>(); for (int i = 0; i<len; i++) list1.add(str[i]); List<String>list2 = new ArrayList<String>(); for (int i = 0; i<len; i++) list2.add(""); Collections.copy(list2,list1); ListIterator<String>iterator = list2.listIterator(); System.out.println("New List..."); while (iterator.hasNext()) System.out.println(iterator.next()); } }
import java.util.LinkedHashSet; public class Demo { public static void main(String[] args) { LinkedHashSet<Integer>set = new LinkedHashSet<Integer>(); set.add(20); set.add(60); set.add(80); set.add(120); set.add(150); set.add(200); set.add(220); set.add(260); set.add(380); System.out.println("Set = "+set); set.remove(150); set.remove(260); System.out.println("Updated Set = "+set); set.remove(60); System.out.println("Updated Set = "+set); } }
import java.util.ArrayList; import java.util.LinkedList; import java.util.List; import java.util.Queue; public class Demo { public static void main(String[] args) { Queue<String>queue = new LinkedList<String>(); queue.add("P"); queue.add("Q"); queue.add("R"); queue.add("S"); queue.add("T"); queue.add("U"); queue.add("V"); List<String>list = new ArrayList<String>(queue); for (Object ob: list) System.out.println(ob); } }
import java.util.HashMap; import java.util.Map; import java.util.Properties; import java.util.Set; public class Demo { public static void main(String args[]) { Properties p = new Properties(); p.setProperty("P", "1"); p.setProperty("Q", "2"); p.setProperty("R", "3"); p.setProperty("S", "4"); p.setProperty("T", "5"); p.setProperty("U", "6"); p.setProperty("V", "7"); HashMap<String, String>map = new HashMap<String, String>((Map) p); Set<Map.Entry<String, String>>set = map.entrySet(); System.out.println("Key and Value of the Map... "); for (Map.Entry<String, String>m: set) { System.out.print(m.getKey() + ": "); System.out.println(m.getValue()); } } }
import java.util.SortedMap; import java.util.TreeMap; public class Demo { public static void main(String[] args) { TreeMap<String, String>tMap = new TreeMap<String,String>(); tMap.put("1", "A"); tMap.put("2", "B"); tMap.put("3", "C"); tMap.put("4", "D"); tMap.put("5", "E"); tMap.put("6", "F"); tMap.put("7", "G"); tMap.put("8", "H"); tMap.put("9", "I"); tMap.put("10", "J"); SortedMap map = tMap.tailMap("2"); System.out.println("Sub Map = " + map); map = tMap.tailMap("8"); System.out.println("Sub Map = " + map); map = tMap.tailMap("1"); System.out.println("Sub Map = " + map); } }
import java.util.Arrays; import java.util.List; public class Demo { public static void main(String[] a) { List<Integer>arrList1 = Arrays.asList(new Integer[] { 10, 20, 30, 45, 55, 70, 90, 100 }); List<Integer>arrList2 = Arrays.asList(new Integer[] {15, 25, 35, 50, 55, 75, 95, 120}); List<Integer>arrList3 = Arrays.asList(new Integer[] { 10, 20, 30, 45, 55, 70, 90, 100}); System.out.println("Are List 1 and List2 equal? "+arrList1.equals(arrList2)); System.out.println("Are List 2 and List3 equal? "+arrList2.equals(arrList2)); System.out.println("Are List 1 and List3 equal? "+arrList1.equals(arrList3)); } }
import java.util.Arrays; import java.util.Collections; import java.util.List; public class Demo { public static void main(String[] args) { List<String>list = Arrays.asList("P","Q","R","P","T","P","U","V","W","X","W" ); int checkOccurrence = Collections.frequency(list, "P"); System.out.println("Occurrence of P = " + checkOccurrence); checkOccurrence = Collections.frequency(list, "W"); System.out.println("Occurrence of W = " + checkOccurrence); checkOccurrence = Collections.frequency(list, "T"); System.out.println("Occurrence of T = " + checkOccurrence); } }
import java.util.ArrayList; public class Demo { public static void main(String[] a) { ArrayList<Integer>arrList = new ArrayList<Integer>(5); arrList.add(100); arrList.add(200); arrList.add(300); arrList.add(400); arrList.add(500); arrList.add(600); arrList.add(700); System.out.println("Size of list = "+arrList.size()); arrList.ensureCapacity(15); for (Integer number: arrList) { System.out.println(number); } arrList.add(100); arrList.add(200); arrList.add(300); arrList.add(400); arrList.add(500); System.out.println("Updated list..."); System.out.println("Size of list = "+arrList.size()); arrList.ensureCapacity(15); for (Integer number: arrList) { System.out.println(number); } } }
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