Java实现Grep

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);
                }
            }
        }
    }
}

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