JAVA EXAMPLE PROGRAMS

JAVA EXAMPLE PROGRAMS

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Reverse a word or string using Stack data structure.


This example uses stack operations to reverse a word (string). First we push each character to the stack, then we will pop each char from the stack.


package com.java2novice.ds.stack;

public class MyWordReverse {

	public String reverseWord(String word){
		
		StringBuilder sb = new StringBuilder();
		int size = word.length();
		StackImpl stack = new StackImpl(size);
		for(int i=0;i<size;i++){
			stack.push(word.charAt(i));
		}
		while(!stack.isStackEmpty()){
			sb.append(stack.pop());
		}
		return sb.toString();
	}
	
	public static void main(String a[]){
		MyWordReverse mwr = new MyWordReverse();
		System.out.println("Java2Novice == "+mwr.reverseWord("Java2Novice"));
		System.out.println("Java == "+mwr.reverseWord("Java"));
		System.out.println("program == "+mwr.reverseWord("program"));
	}
}

class StackImpl {

	private int stackSize;
	private char[] stackArr;
	private int top;

	/**
	 * constructor to create stack with size
	 * @param size
	 */
	public StackImpl(int size) {
		this.stackSize = size;
		this.stackArr = new char[stackSize];
		this.top = -1;
	}

	/**
	 * This method adds new entry to the top 
	 * of the stack
	 * @param entry
	 * @throws Exception 
	 */
	public void push(char entry) {
		this.stackArr[++top] = entry;
	}

	/**
	 * This method removes an entry from the 
	 * top of the stack.
	 * @return
	 * @throws Exception 
	 */
	public char pop() {
		char entry = this.stackArr[top--];
		return entry;
	}
	
	/**
	 * This method returns top of the stack
	 * without removing it.
	 * @return
	 */
	public char peek() {
		return stackArr[top];
	}

	/**
	 * This method returns true if the stack is 
	 * empty
	 * @return
	 */
	public boolean isStackEmpty() {
		return (top == -1);
	}

	/**
	 * This method returns true if the stack is full
	 * @return
	 */
	public boolean isStackFull() {
		return (top == stackSize - 1);
	}
}

Output:
Java2Novice == ecivoN2avaJ
Java == avaJ
program == margorp
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List of Stack Data Structure Examples

  1. Stack introduction & implementation
  2. Java Dynamic Stack Implementation
  3. Stack implementation using generics bounded type.
  4. Reverse a word or string using Stack data structure.
  5. Write a program to find out delimiter matching using stack.
  6. Convert a decimal into a binary number using stack.
  7. Towers of Hanoi implementation using stack.
  8. Evaluation of an infix expression that is fully parenthesized using stack in java.
Knowledge Centre
String Vs StringBuffer
We know that String is immutable object. We can not change the value of a String object once it is initiated. If we try to change the value of the existing String object then it creates new object rather than changing the value of the existing object. So incase, we are going to do more modificatios on String, then use StringBuffer. StringBuffer updates the existing objects value, rather creating new object.
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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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