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diff --git a/Screenshots/program18A.png b/Screenshots/program18A.png
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diff --git a/TestJavaCollection10.java b/TestJavaCollection10.java
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--- /dev/null
+++ b/TestJavaCollection10.java
@@ -0,0 +1,16 @@
+// 17C
+import java.util.*;
+public class TestJavaCollection10{
+  public static void main(String args[]){
+    LinkedHashSet<String> set = new LinkedHashSet<>();
+    set.add("Ravi");
+    set.add("Vijay");
+    set.add(null);
+    set.add("Ravi");
+    set.add("Ajay");
+    Iterator<String> itr = set.iterator();
+    while(itr.hasNext()){
+      System.out.println(itr.next());
+    }
+  }
+}
diff --git a/TestJavaCollection11.java b/TestJavaCollection11.java
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index 0000000..9b852cf
--- /dev/null
+++ b/TestJavaCollection11.java
@@ -0,0 +1,15 @@
+// 18 write a java code to demonstrate treeset
+import java.util.*;
+public class TestJavaCollection11{
+  public static void main(String args[]){
+    TreeSet<String> set = new TreeSet<>();
+    set.add("Ravi");
+    set.add("Vijay");
+    set.add("Ravi");
+    set.add("Ajay");
+    Iterator<String> itr = set.iterator();
+    while(itr.hasNext()){
+      System.out.println(itr.next());
+    }
+  }
+}
diff --git a/TestJavaCollection12.java b/TestJavaCollection12.java
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index 0000000..7372d10
--- /dev/null
+++ b/TestJavaCollection12.java
@@ -0,0 +1,17 @@
+
+// 18B write a java code to demonstrate treeset
+import java.util.*;
+public class TestJavaCollection12{
+  public static void main(String args[]){
+    TreeSet<String> set = new TreeSet<>();
+    set.add("Ravi");
+    set.add("Vijay");
+    set.add(null);
+    set.add("Ravi");
+    set.add("Ajay");
+    Iterator<String> itr = set.iterator();
+    while(itr.hasNext()){
+      System.out.println(itr.next());
+    }
+  }
+}
diff --git a/TestJavaCollection8.java b/TestJavaCollection8.java
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index 0000000..152c718
--- /dev/null
+++ b/TestJavaCollection8.java
@@ -0,0 +1,16 @@
+// 17A write a java code to demonstrate linked hash set
+import java.util.*;
+public class TestJavaCollection8{
+  public static void main(String args[]){
+    LinkedHashSet<String> set = new LinkedHashSet<>();
+    set.add("Ravi");
+    set.add("Vijay");
+    set.add("Ravi");
+    set.add("Ajay");
+    Iterator<String> itr = set.iterator();
+    while(itr.hasNext()){
+      System.out.println(itr.next());
+    }
+  }
+
+}
diff --git a/TestJavaCollection9.java b/TestJavaCollection9.java
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index 0000000..5edc960
--- /dev/null
+++ b/TestJavaCollection9.java
@@ -0,0 +1,17 @@
+// 17B
+import java.util.*;
+public class TestJavaCollection9{
+  public static void main(String args[]){
+    LinkedHashSet<String> set = new LinkedHashSet<>();
+    set.add("Ravi");
+    set.add("Vijay");
+    set.add("");
+    set.add("Ravi");
+    set.add("Ajay");
+    Iterator<String> itr = set.iterator();
+    while(itr.hasNext()){
+      System.out.println(itr.next());
+    }
+  }
+
+}