Java实现Grep

1.[代码]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);

}

}

}

}

}