compareTo

Author: Alan

CompareTo/Main.java

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+import static java.lang.System.*;
+import java.util.*;
+public class Main 
+{
+    static void log(Object o){out.print(o);}
+    static void logLn(Object o){out.println(o);}
+
+    public static void main(String [] args)
+    {
+        TreeSet<User> users = new TreeSet<>();
+        users.add(new User("Kevin", "Nguyen"));
+        users.add(new User("Lyndon", "Nguyen"));
+        users.add(new User("Vince", "Li"));
+        users.add(new User("Alan", "Ngo"));
+        users.add(new User("Varshika", "Pichela"));
+        users.add(new User("Lucinda", "Nguyen"));
+        users.add(new User("Carlos", "Ovalle"));
+        users.add(new User("Smruti", "Shah"));
+
+        logLn(users);
+        // Should print
+        // [Alan Ngo, Carlos Ovalle, Kevin Nguyen, Lucinda Nguyen, Lyndon Nguyen, Varshika Pichela, Vince Li, Smruti Shah]
+    }
+}

CompareTo/README.md

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+# Comparing Objects
+
+#### class needs to implement java.lang.Comparable
+
+```java
+public class Student implements Comparable<Student>
+{
+    ...
+}
+```
+
+useful for 
+- sorting
+- TreeSet
+- TreeMap
+
+Need to implement
+
+```java
+@Override
+public int compareTo(Student arg0) 
+{
+    if (arg0 == this)
+        return 0;
+    
+    // logic goes here
+    ...
+}
+```

CompareTo/User.java

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+import static java.util.Objects.*;
+public class User implements Comparable<User>
+{
+    private final String firstName;
+    private final String lastName;
+
+    public User(String fN, String lN)
+    {
+        firstName = fN;
+        lastName = lN;
+    }
+
+
+    // overriden from java.lang.Object
+    @Override
+    public String toString(){return firstName+" "+ lastName;}
+
+    @Override
+    public boolean equals(Object o)
+    {
+        if (!(o instanceof User))
+            return false;
+
+        if (o == this)
+            return true;
+
+        User u = (User) o;
+        return this.firstName.equals(u.firstName)
+        && this.lastName.equals(u.lastName);
+    }
+
+    @Override
+    public int hashCode(){return hash(firstName, lastName);}
+
+    //overriden from java.lang.Comparable
+    @Override
+    public int compareTo(User arg0) 
+    {
+        if (arg0 == this)
+            return 0;
+        
+        // we want to sort by first AND last name
+        return this.firstName.compareTo(arg0.firstName)+
+        this.lastName.compareTo(arg0.lastName);
+    }
+
+}