文件名称：java io读取文件到String
文件大小：212KB
文件格式：MHT
更新时间：2015-11-28 15:28:48
java io读取文件 String
public static String loadAFileToStringDE1(File f) throws IOException { long beginTime = System.currentTimeMillis(); InputStream is = null; String ret = null; try { is = new BufferedInputStream( new FileInputStream(f) ); long contentLength = f.length(); ByteArrayOutputStream outstream = new ByteArrayOutputStream( contentLength > 0 ? (int) contentLength : 1024); byte[] buffer = new byte[4096]; int len; while ((len = is.read(buffer)) > 0) { outstream.write(buffer, 0, len); } outstream.close(); ret = outstream.toString(); //byte[] ba = outstream.toByteArray(); //ret = new String(ba); } finally { if(is!=null) {try{is.close();} catch(Exception e){} } } long endTime = System.currentTimeMillis(); System.out.println("方法1用时"+ (endTime-beginTime) + "ms"); return ret; } public static String loadAFileToStringDE2(File f) throws IOException { long beginTime = System.currentTimeMillis(); InputStream is = null; String ret = null; try { is = new FileInputStream(f) ; long contentLength = f.length(); byte[] ba = new byte[(int)contentLength]; is.read(ba); ret = new String(ba); } finally { if(is!=null) {try{is.close();} catch(Exception e){} } } long endTime = System.currentTimeMillis(); System.out.println("方法2用时"+ (endTime-beginTime) + "ms"); return ret; } public static String loadAFileToStringDE3(File f) throws IOException { long beginTime = System.currentTimeMillis(); BufferedReader br = null; String ret = null; try { br = new BufferedReader(new FileReader(f)); String line = null; StringBuffer sb = new StringBuffer((int)f.length()); while( (line = br.readLine() ) != null ) { sb.append(line).append(LINE_BREAK); } ret = sb.toString(); } finally { if(br!=null) {try{br.close();} catch(Exception e){} } } long endTime = System.currentTimeMillis(); System.out.println("方法3用时"+ (endTime-beginTime) + "ms"); return ret; } 3个方法去读取一个大于50M的文件，当不设置jvm参数时都OutofMemery，当设置-Xmx128M时。只有方法3 可以通过，设置到-Xmx256M时也只有方法3可以通过，干脆设置512M，都可以了，运行时间如果正常的话一般都在4～5S