palindrometest.java

字符串回文简便算法,JAVA代码,包括自动处理空格标点符号以及其他字符串等.

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class PalindromeTest {
      
    private boolean flag = false;   

    public PalindromeTest() 
    {   
    }   
    //loop compare method
    public boolean Iterrative(String str) 
    {
    	for (int i = 0; i < str.length()/2; i++)//loop entry condition
    	{
            if (str.charAt(i) != str.charAt(str.length() - i - 1)) 
            { //use charAt method to compare
                return false;
            }
        }
        return true;
    }
    //makes calls to itself
    public boolean Recursive(String str) //the Recursive method
    {   
        if (str.length() == 1) // must be a palindrome 
        {   
          this.flag = true;   
        }   
        else
        {
          if(str.substring(0,1).equals(
        		  str.substring(str.length()-1, str.length())))   
          { //check each two character from the first and the last 
        	  
            String temp = str.substring(1, str.length()-1);
            if(temp.length() > 0)
            {
              this.flag = true;
        	  Recursive(temp); 
            }
          }   
          else   
          {   
            this.flag = false;   
          }   
        }
        return this.flag;      
    }
	public static void main(String[] args) throws IOException {
		//Declaration
		BufferedReader input = new BufferedReader
			(new InputStreamReader(System.in));
		String inputLine;
		PalindromeTest pt = new PalindromeTest();
		System.out.print("Please input a line of text: ");
		inputLine = input.readLine();
		inputLine = inputLine.toLowerCase();
       
		while(inputLine.length() > 0)
		{
		  //
		  //handle spaces and punctuation marks
		  //
	      //use regular expressions 
	      Pattern p = Pattern.compile("[.,\"\\?!:;<>']");//punctuation marks
	      Matcher m = p.matcher(inputLine);
	      String first = m.replaceAll("");//replace all punctuation marks
	      p = Pattern.compile("\\s");
	      m = p.matcher(first);
	      String second = m.replaceAll("");//replace spaces

	      inputLine = second;
		  
	      if(inputLine.length() > 0)
	      {
	    	//call two different methods to check
		    if(pt.Iterrative(inputLine))
		    {
		      System.out.println("Iterative version: This is a palindrome!");
		    }
		    else
		    {
		      System.out.println("Iterative version: This is not a palindrome!");
		    }
		    if(pt.Recursive(inputLine))
		    {
		      System.out.println("Recursive version: This is a palindrome!");
		    }
		    else
		    {
			  System.out.println("Recursive version: This is not a palindrome!");
		    }
	      }
	      else
	      {
	    	  System.out.println("All you input are punctuation and space!");
	      }
	      System.out.println("");
		  System.out.print("Please input a line of text: ");
		  inputLine = input.readLine();
		  inputLine = inputLine.toLowerCase();
		}
		if(inputLine.length() == 0)	//if blank line
		{
		  System.out.println("Program terminated!");
		}
	}
}