Java实现Grep详解编程语言

Java实现Grep

grep.java

import java.io.*; 
public class grep{ 
    public static void main(String [] args) throws IOException{ 
        if(args.length<1){ 
            System.out.println("zu wenige Parameter"); 
            throw new IllegalArgumentException("zu wenig Parameter!"); 
        } 
        boolean reversed =false; 
        String pattern; 
        String sfile =""; 
        try{ 
        if(args[0].equals("-v")){ 
            reversed = true; 
            pattern =args[1]; 
            if(args.length>2){ 
                sfile = args[2]; 
            } 
        }else{ 
            pattern = args[0]; 
            if(args.length==2){ 
                sfile = args[1]; 
            } 
        } 
        }catch(IndexOutOfBoundsException ex){ 
            System.out.println("Irgendwas ist beim verarbeiten der Parameter schiefgegangen: " + ex); 
            return; 
        } 
        if (!(sfile.equals(""))){ 
            File myfile; 
            try{ 
                myfile = new File(sfile); 
            }catch(NullPointerException ex){ 
                System.out.println("uhhps das sollte nicht passieren: " + ex); 
                return; 
            } 
            BufferedReader myreader; 
            try{ 
            myreader = new BufferedReader(new FileReader(myfile)); 
            }catch(FileNotFoundException ex){ 
                System.out.println("File Not Found: " + ex); 
                return; 
            } 
            search(myreader, reversed, pattern); 
        }else{ 
            BufferedReader myreader = new BufferedReader(new InputStreamReader(System.in)); 
            try{ 
                search(myreader, reversed, pattern); 
            }catch(IOException ex){ 
                System.out.println("IO Fehler: " +ex); 
            } 
        } 
 
    } 
    private static void search(BufferedReader myreader, boolean reversed, String pattern) throws IOException{ 
        //System.out.println("Suche nach: " + pattern); 
        while(myreader.ready()){ 
            String sline = myreader.readLine(); 
            if (reversed){ 
                if(!sline.contains(pattern)){ 
                    System.out.println(sline); 
                } 
            }else{ 
                if (sline.contains(pattern)){ 
                    System.out.println(sline); 
                } 
            } 
        } 
    } 
}