Map and Set Demos

Collections/MapDemo.java

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+import java.util.HashMap;
+import java.util.TreeSet;
+
+
+public class MapDemo {
+
+	public static void main(String[] args) {
+		HashMap<String,Object> map = new HashMap<>();
+		TreeSet<Integer> amitPhones = new TreeSet<>();
+		amitPhones.add(2222);
+		amitPhones.add(2222);
+		amitPhones.add(3333);
+		map.put("amit", amitPhones);
+		//map.put("amit",3333);
+		map.put("ram", 3333);
+		System.out.println(map.get("amit"));
+		System.out.println(map);
+
+
+	}
+
+}

Collections/SetDemo.java

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+import java.util.HashSet;
+
+class Customer
+{
+	int id;
+	String name;
+	Customer(int id , String name){
+		this.id = id ;
+		this.name = name;
+	}
+	public String toString(){
+		return "Id "+id +" Name "+name;
+	}
+
+	public boolean equals(Object o){
+		Customer c = (Customer) o;
+		if(this.id==c.id && this.name.equals(c.name)){
+			return true;
+		}
+		else
+		{
+			return false;
+		}
+	}
+
+	@Override
+	public int hashCode(){
+		return name.length();
+	}
+}
+public class SetDemo {
+
+	public static void main(String[] args) {
+		Customer ram = new Customer(1001,"Ram");
+		HashSet<Customer> hashSet = new HashSet<>();
+		hashSet.add(ram);
+		Customer ram2 = new Customer(1001,"Ram");
+		hashSet.add(ram2);
+		System.out.println("Ram HashCode "+ram.hashCode());
+		System.out.println("Ram2 HashCode  "+ram2.hashCode());
+		System.out.println(hashSet);
+
+
+
+	}
+
+}

Collections/SimpleSet.java

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+import java.util.HashSet;
+
+
+public class SimpleSet {
+
+	public static void main(String[] args) {
+		HashSet<String> hs = new HashSet<String>();
+		hs.add("mike");
+		hs.add("tim");
+		hs.add("mike");
+		hs.add("tim");
+		System.out.println(hs);
+	}
+
+}