Java ListResourceBundle handleKeySet() Method

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Description

The Java ListResourceBundle handleKeySet() method returns a Set of the keys contained only in this ResourceBundle.

Declaration

Following is the declaration for java.util.ListResourceBundle.handleKeySet() method

protected Set<String> handleKeySet()

Parameters

NA

Return Value

This method returns a Set of the keys contained only in this ResourceBundle.

Exception

NA

Getting Set of Keys of a ListResourceBundle of String, Integer Pair Example

The following example shows the usage of Java ListResourceBundle handleKeySet() method to iterate keys of the ListResourceBundle. We've created a ListResourceBundle object having contents an two dimensional array of String, Integer pairs. Then few entries are added by overriding getContents() method and then an enumeration of keys is retrieved in overridden handleKeySet() method and iterated to get the keys. In main method, we're getting the Set of Keys using handleKeySet() method.

package com.tutorialspoint;

import java.util.Enumeration;
import java.util.HashSet;
import java.util.ListResourceBundle;
import java.util.Set;

// create a class that extends to ListResourceBundle
class MyResources extends ListResourceBundle {

   // get contents must be implemented
   protected Object[][] getContents() {
      return new Object[][] {
         {"1", 1},
         {"2", 2},
         {"3", 3}
      };
   }

   protected Set<String> handleKeySet() {
      Set<String> set = new HashSet<String>();

      // get the keys
      Enumeration<String> enumeration = getKeys();

      // print the keys
      while (enumeration.hasMoreElements()) {
         set.add(enumeration.nextElement());
      }
      return set;
   }
}

public class ListResourceBundleDemo {
   public static void main(String[] args) {

      // create a new MyResources instance
      MyResources mr = new MyResources();

      // get the set of Keys
      Set<String> keys = mr.handleKeySet();

      // print each key
      keys.forEach(System.out::println);
   }
}

Output

Let us compile and run the above program, this will produce the following result.

1
2
3

Getting Set of Keys of a ListResourceBundle of String, String Pair Example

The following example shows the usage of Java ListResourceBundle handleKeySet() method to iterate keys of the ListResourceBundle. We've created a ListResourceBundle object having contents an two dimensional array of String, String pairs. Then few entries are added by overriding getContents() method and then an enumeration of keys is retrieved in overridden handleKeySet() method and iterated to get the keys. In main method, we're getting the Set of Keys using handleKeySet() method.

package com.tutorialspoint;

import java.util.Enumeration;
import java.util.HashSet;
import java.util.ListResourceBundle;
import java.util.Set;

// create a class that extends to ListResourceBundle
class MyResources extends ListResourceBundle {

   // get contents must be implemented
   protected Object[][] getContents() {
      return new Object[][] {
         {"1", "Hello World!"},
         {"2", "Goodbye World!"},
         {"3", "Goodnight World!"}
      };
   }

   protected Set<String> handleKeySet() {
      Set<String> set = new HashSet<String>();

      // get the keys
      Enumeration<String> enumeration = getKeys();

      // print the keys
      while (enumeration.hasMoreElements()) {
         set.add(enumeration.nextElement());
      }
      return set;
   }
}

public class ListResourceBundleDemo {
   public static void main(String[] args) {

      // create a new MyResources instance
      MyResources mr = new MyResources();

      // get the set of Keys
      Set<String> keys = mr.handleKeySet();

      // print each key
      keys.forEach(System.out::println);
   }
}

Output

Let us compile and run the above program, this will produce the following result.

1
2
3

Getting Set of Keys of a ListResourceBundle of String, Object Pair Example

The following example shows the usage of Java ListResourceBundle handleKeySet() method to iterate keys of the ListResourceBundle. We've created a ListResourceBundle object having contents an two dimensional array of String, Student pairs. Then few entries are added by overriding getContents() method and then an enumeration of keys is retrieved in overridden handleKeySet() method and iterated to get the keys. In main method, we're getting the Set of Keys using handleKeySet() method.

package com.tutorialspoint;

import java.util.Enumeration;
import java.util.HashSet;
import java.util.ListResourceBundle;
import java.util.Set;

// create a class that extends to ListResourceBundle
class MyResources extends ListResourceBundle {

   // get contents must be implemented
   protected Object[][] getContents() {
      return new Object[][] {
         {"1", new Student(1, "Julie")},
         {"2", new Student(2, "Robert")},
         {"3", new Student(3, "Adam")}
      };
   }

   protected Set<String> handleKeySet() {
      Set<String> set = new HashSet<String>();

      // get the keys
      Enumeration<String> enumeration = getKeys();

      // print the keys
      while (enumeration.hasMoreElements()) {
         set.add(enumeration.nextElement());
      }
      return set;
   }
}

public class ListResourceBundleDemo {
   public static void main(String[] args) {

      // create a new MyResources instance
      MyResources mr = new MyResources();

      // get the set of Keys
      Set<String> keys = mr.handleKeySet();

      // print each key
      keys.forEach(System.out::println);
   }
}

class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
}

Output

Let us compile and run the above program, this will produce the following result.

1
2
3