JAVA EXAMPLE PROGRAMS

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Program: How to search a key in HashMap?


Description:

Below example shows how to find whether specified key exists or not. By using containsKey() method you can find out the key existance.


Code:
package com.java2novice.hashmap;

import java.util.HashMap;

public class MyHashMapKeySearch {
	
	public static void main(String a[]){
		HashMap<String, String> hm = new HashMap<String, String>();
		//add key-value pair to hashmap
		hm.put("first", "FIRST INSERTED");
		hm.put("second", "SECOND INSERTED");
		hm.put("third","THIRD INSERTED");
		System.out.println(hm);
		if(hm.containsKey("first")){
			System.out.println("The hashmap contains key first");
		} else {
			System.out.println("The hashmap does not contains key first");
		}
		if(hm.containsKey("fifth")){
			System.out.println("The hashmap contains key fifth");
		} else {
			System.out.println("The hashmap does not contains key fifth");
		}
	}
}

Output:
{second=SECOND INSERTED, third=THIRD INSERTED, first=FIRST INSERTED}
The hashmap contains key first
The hashmap does not contains key fifth
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List Of All HashMap Sample Programs:

  1. Basic HashMap Operations.
  2. How to iterate through HashMap?
  3. How to copy Map content to another HashMap?
  4. How to search a key in HashMap?
  5. How to search a value in HashMap?
  6. How to get all keys from HashMap?
  7. How to get entry set from HashMap?
  8. How to delete all elements from HashMap?
  9. How to eliminate duplicate user defined objects as a key from HashMap?
  10. How to find user defined objects as a key from HashMap?
  11. How to delete user defined objects as a key from HashMap?
Knowledge Centre
Can we call servlet destory() from service()?
As you know, destory() is part of servlet life cycle methods, it is used to kill the servlet instance. Servlet Engine is used to call destory(). In case, if you call destory method from service(), it just execute the code written in the destory(), but it wont kill the servlet instance. destroy() will be called before killing the servlet instance by servlet engine.
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About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected].

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java™ Platform Standard Ed. 8 - API Specification | Java is registered trademark of Oracle.
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