JAVA EXAMPLE PROGRAMS

JAVA EXAMPLE PROGRAMS

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Write a program to find out delimiter matching using stack.


One of the common use of the stacks is to parse certain kinds of expressions or string text. Write a program that verifies the delimiters in a line of text or expression typed by the user. In this case we will take an arthimetic expression like a*(b+c)+[c/(a-b)]. We need to validate the expression such that the opening and closing brackets are proper or not.

a*(b+c) //This expression is right

b/[a*(b+c)] //This expression is right

{a*(b+c]} //This expression is wrong

package com.java2novice.ds.stack;

public class MyDelimiterMatching {

	public static void main(String a[]){
		MyDelimiterMatching mdm = new MyDelimiterMatching();
		String expression = "{(a+b)*(c+d)}";
		boolean result = mdm.isDelimiterMatching(expression);
		System.out.println(expression +" == "+result);
		
		expression = "{(a+b)+[x*(c+d)]}";
		result = mdm.isDelimiterMatching(expression);
		System.out.println(expression +" == "+result);
		
		expression = "{(a+b)+[x*(c+d)}}";
		result = mdm.isDelimiterMatching(expression);
		System.out.println(expression +" == "+result);
	}

	public boolean isDelimiterMatching(String inputExpr) {
		
		int stackSize = inputExpr.length();
		StackImpl theStack = new StackImpl(stackSize);
		for (int j = 0; j < inputExpr.length(); j++) {
			char ch = inputExpr.charAt(j);
			switch (ch) {
			case '{':
			case '[':
			case '(':
					theStack.push(ch);
					break;
			case '}':
			case ']':
			case ')':
					if (!theStack.isStackEmpty()) {
						char stackContent = theStack.pop();
						if ((ch == '}' && stackContent != '{') 
								|| (ch == ']' && stackContent != '[')
								|| (ch == ')' && stackContent != '(')){
							System.out.println("Mismatch found: " + ch + " at " + j);
							return false;
						}
					} else {
						System.out.println("Mismatch found: " + ch + " at " + j);
						return false;
					}
					break;
			default: break;
			}
		}
		if (!theStack.isStackEmpty()){
			System.out.println("Error: missing right delimiter");
			return false;
		}
		return true;
	}
}


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:
{(a+b)*(c+d)} == true
{(a+b)+[x*(c+d)]} == true
Mismatch found: } at 15
{(a+b)+[x*(c+d)}} == false
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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.
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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java is registered trademark of Oracle.
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