grep.java

Implementation of the popular Grep program, from most linux systems, written in 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);
				}
			}
		}
	}
}