Java: // usage of Comparator and Comparable (output the key-value pairs of the map set in sequence as required ),

Java: // usage of Comparator and Comparable (output the key-value pairs of the map set in sequence as required ),

 

Import java. util .*;

Public class Person implements Comparable <Person> // compare the attributes of Person.

{

Private String name;

Private int age;

Public Person (String name, int age) // initialize the constructor

{

This. name = name;

This. age = age;

}

Public void set (String name, int age) // reset the name and age

{

This. name = name;

This. age = age;

}

Public String getName () // get the name

{

Return name;

}

 

Public int getAge () // get age

{

Return age;

}

Public String toString () // returns the name and age in the form of a String

{

Return name + "," + age;

}

// When duplicate names occur, find another hash address to store data (automatically called at the underlying layer)

Public int hashCode ()

{

Return name. hashCode () + age * 34;

}

// Determine whether the accepted class is a Person class. If not, an exception is thrown (automatically called at the underlying layer)

Public boolean equals (Object obj)

{

If (! (Obj instanceof Person ))

Throw new ClassCastException ("not a Person class ");

Person p = (Person) obj;

Return this. name. equals (p. name) & this. age = p. age;

}

Public int compareTo (Person p) // (compare according to your own requirements)

{

Int num = new Integer (this. age). compareTo (p. age );

Return num = 0? This. name. compareTo (p. name): num;

}

}

Public class Test

{

Public static <T> void sop (T t)

{

System. out. println (t );

}

Public static void main (String args []) throws Exception

{

// Create a map set to store data <> indicates that the received data is generic, that is, the specified type.

TreeMap <Person, String> map = new TreeMap <Person, String> (/* new Mycompare ()*/);

// Add data to the set

Map. put (new Person ("czhangsan1", 11), "beijing ");

Map. put (new Person ("zhangsan5", 15), "nanjing ");

Map. put (new Person ("azhangsan5", 10), "shanghai ");

Map. put (new Person ("zhangsan2", 20), "haierbing ");

Map. put (new Person ("bzhangsan2", 20), "beijing ");

Map. put (new Person ("zhangsan3", 12), "shanghai ");

Map. put (new Person ("zhangsan4", 19), "changchun ");

Map. put (new Person ("zhangsan4", 10), "changchun ");

Map. put (new Person ("zhangsan4", 10), "zhengzhou ");

// Converts a map set to a set, because there is no iterator for the map set, and the set has

Set <Map. Entry <Person, String> entryset = map. entrySet ();

// Obtain the iterator

Iterator <Map. Entry <Person, String> it = entryset. iterator ();

// Use the iterator to retrieve data

While (it. hasNext ())

{

Map. Entry <Person, String> m = it. next ();

Person key = m. getKey (); // retrieve key

String value = m. getValue (); // retrieves the value.

Sop (key + "..." + "adress:" + value); // print the key and value

}

}

}

Class Mycompare implements comparator <Perosn> // customize a comparator

{

Public int compare (Person p1, Person p2)

{

Int num = p1.getName (). compareTo (p2.getName ());

Return num = 0? New Integer (p1.getAge (). compareTo (new Integer (p2.getAge (): num;

}

}

// Note: Both of the above two forms achieve comparison. You can select either of them. Either implement the comparable interface or pass in a custom comparator in the set.