• 프로그램 문법
• Java 기초
• 상수/변수 선언
• 연산자
• 조건문/반복문
• 오류 처리
• 코드 변환
• 기타 사항
• 입출력
• 브라우저 입출력
• Cookie 입출력
• Session 입출력
• Container 입출력
• 콘솔 입출력
• 파일 입출력
• Excel File 입출력
• Java Reflection
• Shutdown 관리
• 자주 사용하는 Class
• HashMap
• ArrayList
• 사용자 정의 라이브러리
• 윈도우 Command Line에서 Java 프로그램 실행
• DES 암복호화
• RSA 암복호화
• 사용자 정의 프로그램
• HTML에서 원하는 문자열 추출
• UUID 생성
• Java 8
• 람다식 (Lambda Expression)
• Stream (Java Collection API)
• Nashorn
• 문제 해결
• 관련 자료
• Java Decompiler
• 참고 문헌

Java, Servlet, JSP에 대한 기본적인 사항을 정리한다.

프로그램 문법

---

Java 기초

• 주석

 //  한줄 짜리 주석
 /*  여러줄 짜리 주석  */

상수/변수 선언

• 변수의 선언/삭제 및 적용 범위

연산자

조건문/반복문

오류 처리

• 오류 수집

 try {
 } catch(ex) {
 } finally {
 }

코드 변환

• UTF-8로 인코딩 parameter을 서버(Java)에서 받는 방법

 request.setCharacterEncoding("utf-8");
 String name = request.getParameter("name");

기타 사항

입출력

---

브라우저 입출력

• URL

 URL url = null;
 HttpURLConnection conn = null;
 //BufferedWriter out = null;
 PrintWriter out = null;
 BufferedReader inp = null;
 String buf = null;
 
 try {
     url = new URL(requestURL);
     conn = (HttpURLConnection) url.openConnection();
     conn.setRequestMethod("POST");
     conn.setRequestProperty("Content-type", "application/x-www-form-urlencoded");
     conn.setDoOutput(true);
     conn.setDoInput(true);
     
     //out = new BufferedWriter(new OutputStreamWriter(conn.getOutputStream()));
     out = new PrintWriter(new OutputStreamWriter(conn.getOutputStream(), "8859_1"), true);
     out.write("Post data");
     out.flush();
     
     if (conn.getResponseCode() == HttpURLConnection.HTTP_OK) {
         inp = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
         while ((buf = inp.readLine()) != null) {
             System.out.println(buf);
         }
     } else {
         System.out.println("Bad post ... : " + conn.getResponseCode() + " : " + conn.getResponseMessage());
     }
     inp.close();
     out.close();
 } catch (MalformedURLException e) {
     System.out.println(e);
     return false;
 } catch (IOException e) {
     System.out.println(e);
     return false;
 } finally {
     if (inp != null) {
     try { inp.close(); } catch (IOException e) { }
     inp = null;
 }
 
 if (out != null) {
 try { out.close(); } catch (Exception e) { }
 out = null;
 }
 }

Cookie 입출력

• Cookie 조회

 private String getCookie(HttpServletRequest req, String name)
 {
     String rtStr = null; 
     Cookie cookies[](.md) = null;
 
     cookies = req.getCookies();
     for (int idx = 0;idx < cookies.length;idx++) {
         if (cookies[idx](idx.md).getName().equals(name)) {
         	rtStr = cookies[idx](idx.md).getValue();
         	break;
         }
     }
     return rtStr;
 }

• Cookie 등록

 Cookie cookie = new Cookie("username", name);
 cookie.setMaxAge(30*60);  //30분...
 response.addCookie(cookie);

Session 입출력

Container 입출력

콘솔 입출력

파일 입출력

 String inputLine = null;
 File tmpFile = null;
 BufferedReader inp = null;
 
 tmpFile = new File("/docs/hello.html");
 try {
     inp = new BufferedReader(new FileReader(tmpFile));
     while ((inputLine = inp.readLine()) != null) {
     }
 } catch (FileNotFoundException e) {
     e.printStackTrace();
 } catch (IOException e) {
     e.printStackTrace();
 } finally {
     if (inp != null) {
         try {
             inp.close();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
     inp = null;
 }

Excel File 입출력

• Library

  • Java Excel API : http://www.andykhan.com/jexcelapi/
  • POI : http://jakarta.apache.org/poi/index.html

• UtilExcel.java with POI

 package com.jopenbusiness.util;
 
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
 
 import org.apache.poi.ss.usermodel.Cell;
 import org.apache.poi.ss.usermodel.DateUtil;
 import org.apache.poi.xssf.usermodel.XSSFCell;
 import org.apache.poi.xssf.usermodel.XSSFRow;
 import org.apache.poi.xssf.usermodel.XSSFSheet;
 import org.apache.poi.xssf.usermodel.XSSFWorkbook;
 
 //---	HSSF : ~.xls, XSSF : ~.xlsx 
 public class UtilExcel {
     public static XSSFWorkbook getWorkbook(String fileName) { 
         try { 
             return new XSSFWorkbook(new FileInputStream(new File (fileName)));
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
         return null;
     }
      
     public static XSSFSheet getSheet(String fileName, String sheetName) {
         XSSFWorkbook excel = null;
         
         excel = getWorkbook(fileName);
         return (excel == null) ? null:excel.getSheet(sheetName);
     }
      
     public static XSSFCell getCell(XSSFSheet sheet, Integer idxRow, Integer idxCol) {
         XSSFRow row = null;
         
         row = sheet.getRow(idxRow);
         return (row == null) ? null:row.getCell(idxCol);
     }
  
     public static String getCellType(XSSFCell cell) {
         if (cell == null) {
             return "String";
         }
         switch (cell.getCellType()) {
         case Cell.CELL_TYPE_NUMERIC : return (DateUtil.isCellDateFormatted(cell)) ? "Date/" + cell.getCellType():"Numeric/" + cell.getCellType();
         case Cell.CELL_TYPE_STRING 	: return "String/" + cell.getCellType();
         case Cell.CELL_TYPE_FORMULA : return "Formula/" + cell.getCellType();
         case Cell.CELL_TYPE_BOOLEAN : return "Boolean/" + cell.getCellType();
 
         case Cell.CELL_TYPE_BLANK 	: return "Blank/" + cell.getCellType();
         case Cell.CELL_TYPE_ERROR 	: return "Error/" + cell.getCellType();
         default 					: return "Other/" + cell.getCellType();
         }
     }
  
     public static String getCellType(XSSFSheet sheet, Integer idxRow, Integer idxCol) {
         return getCellType(getCell(sheet, idxRow, idxCol));
     }
  
     public static String getCellString(XSSFCell cell, String defaultValue) {
         String rtStr = null;
  
         if (cell == null) {
             return defaultValue;
         }
          
         switch (cell.getCellType()) {
         case Cell.CELL_TYPE_STRING :
             rtStr = cell.getStringCellValue();
             break;
         case Cell.CELL_TYPE_NUMERIC :
             if (DateUtil.isCellDateFormatted(cell)) {
                 rtStr = UtilDate.getFormattedDate(cell.getDateCellValue(), UtilDate.SIMPLE_DATE_FORMAT);
             } else {
                 rtStr = String.valueOf(cell.getNumericCellValue());
             }
             break;
         case Cell.CELL_TYPE_BOOLEAN :
             rtStr = (cell.getBooleanCellValue()) ? "true":"false";
             break;
         case Cell.CELL_TYPE_FORMULA :
 //			rtStr = cell.getCellFormula();
              rtStr = cell.getRawValue();
              break;
         case Cell.CELL_TYPE_BLANK :
             rtStr = cell.getStringCellValue();
             break;
         case Cell.CELL_TYPE_ERROR :
             rtStr = cell.getErrorCellString();
             break;
         default :
             rtStr = "/" + cell.getCellType() + "/" + cell.toString() + "/";
         }
         return rtStr;
     }
  
     public static String getCellString(XSSFCell cell) {
         return getCellString(cell, "");
     }
      
     public static String getCellString(XSSFSheet sheet, Integer idxRow, Integer idxCol, String defaultValue) {
         return getCellString(getCell(sheet, idxRow, idxCol), defaultValue);
     }
  
     public static String getCellString(XSSFSheet sheet, Integer idxRow, Integer idxCol) {
         return getCellString(sheet, idxRow, idxCol, "");
     }
      
     public static List getRowStrings(XSSFSheet sheet, Integer idxRow, Integer idxColFr, Integer idxColTo) {
         List rtList = null;
          
         rtList = new ArrayList();
         for (Integer idx = idxColFr;idx <= idxColTo;idx++) {
             rtList.add(getCellString(sheet, idxRow, idx));
         }
         return rtList;
     }
      
     public static List> getTableStrings(XSSFSheet sheet, Integer idxColFr, Integer idxColTo) {
         List> rtList = null;
         List rowList = null;
         Integer cntSkip = null;
         Integer idxRow = null;
         String tmpApply = null;
  
         idxRow = 0;
         cntSkip = 0;
         rtList = new ArrayList>();
         while (true) {
             rowList = getRowStrings(sheet, idxRow, idxColFr, idxColTo);
             if (sheet.getLastRowNum() < idxRow) {
                 break;
             }
             idxRow++;
 
             tmpApply = rowList.get(0);
             if ((tmpApply != null) && (tmpApply.equalsIgnoreCase("End Table"))) {
                 break;
             }
              
             if ((tmpApply == null) || (!tmpApply.equals("적용"))) {
                 cntSkip = cntSkip + 1;
                 if (100 < cntSkip) {
                     break;
                 }
                 continue;
             }			
             cntSkip = 0;
             rtList.add(rowList);
         }
         return rtList;
     }
  
     public static List findRowStrings(XSSFSheet sheet, Integer findIdx, String findStr, Integer idxColFr, Integer idxColTo) {
          String tmpStr = null;
 
         for (Integer idx = sheet.getFirstRowNum();idx <= sheet.getLastRowNum();idx++) {
             tmpStr = getCellString(sheet, idx, findIdx);
             if ((tmpStr != null) && (tmpStr.equals(findStr))) {
                 return getRowStrings(sheet, idx, idxColFr, idxColTo);
             }
         }		
         return null;
     }
      
     public static String toString(List dataStr) {
         String rtStr = null;
         
         for (String item : dataStr) {
             rtStr = (rtStr == null) ? "":rtStr + ", ";
             rtStr = rtStr + "[+ item + "](")";
         }
         return rtStr;
     }
  }

Java Reflection

---

Java에서 제공하는 Java Reflection 기능을 사용하면 동적으로 Class, Method를 관리할 수 있다.

• Java Reflection Class (rt.jar)

  • sun.reflect
    • Reflection, ReflectionFactory
  • sun.refletc.misc
    • ConstructorUtil, FieldUtil, MethodUtil, ReflectUtil, Trampoline

• 사용 예 1

         try {
            Class c = Class.forName(args[0](0.md)); //---  c = String.class
            Method m[](.md) = c.getDeclaredMethods();
  //--- getDeclaredMethods()메소드 대신 getMethods()를 사용하게 되면, 상속된 메소드의 정보까지 얻을수있다.
            for (int i = 0; i < m.length; i++)
            System.out.println(m[i](i.md).toString());
         }
         catch (Throwable e) {
            System.err.println(e);
         }

  //--- 생성자 반환
     Constructor ctorlist[](.md)
               = cls.getDeclaredConstructors();

    Class cls = Class.forName("A");
            boolean b1 
              = cls.isInstance(new Integer(37));

  Field fieldlist[](.md) 
              = cls.getDeclaredFields();

 //-- Method 실행
        Class cls = Class.forName("method2");
           Class partypes[] = new Class[2](2.md);
            partypes[0](0.md) = Integer.TYPE;
            partypes[1](1.md) = Integer.TYPE;
            Method meth = cls.getMethod(
              "add", partypes);
            method2 methobj = new method2();
            Object arglist[] = new Object[2](2.md);
            arglist[0](0.md) = new Integer(37);
            arglist[1](1.md) = new Integer(47);
            Object retobj 
              = meth.invoke(methobj, arglist);
            Integer retval = (Integer)retobj;
            System.out.println(retval.intValue());

 //--- 클래스 생성
           Class cls = Class.forName("constructor2");
           Class partypes[] = new Class[2](2.md);
            partypes[0](0.md) = Integer.TYPE;
            partypes[1](1.md) = Integer.TYPE;
            Constructor ct 
              = cls.getConstructor(partypes);
            Object arglist[] = new Object[2](2.md);
            arglist[0](0.md) = new Integer(37);
            arglist[1](1.md) = new Integer(47);
            Object retobj = ct.newInstance(arglist);

 //--- 배열 관리
      try {
            Class cls = Class.forName(
              "java.lang.String");
            Object arr = Array.newInstance(cls, 10);
            Array.set(arr, 5, "this is a test");
            String s = (String)Array.get(arr, 5);
            System.out.println(s);

• 참고 문헌
  • http://lovelyjk.tistory.com/30

Shutdown 관리

---

• Shutdown 상황
  • Throwable
    • Exception, Error
  • SIGINT : Ctrl_C, ShutdownHook 호출됨
  • SIGTERM : kill ~, ShutdownHook 호출됨
  • SIGKILL : kill -9 ~

자주 사용하는 Class

---

HashMap

 HashMap map = new HashMap();
 
 map.put("name", "value");
 for (Map.Entry entry : processInfo.entrySet()) {
    entry.getKey(), entry.getValue()
 }

ArrayList

사용자 정의 라이브러리

---

윈도우 Command Line에서 Java 프로그램 실행

• extractHtml.vbs (WScript 파일)

 '===============================================================================
 '       프로그램 명     : /extractHtml.vbs
 '       프로그램 설명   : Java를 컴파일하고 실행하기 위한 스크립트
 '       작성자          : 산사랑
 '       작성일          : 2008.07.08 ~ 2008.07.08
 '------ [관리](History) ---------------------------------------------------------
 '       수정자          :
 '       수정일          :
 '       수정 내용       :
 '------ [Copyright](Copyright.md) ------------------------------------------------------------
 '      Copyright (c) 1995-2008 pnuskgh, All rights reserved.
 '===============================================================================
 On Error Resume Next
 
 '-------------------------------------------------------------------------------
 '       Main Routine
 '-------------------------------------------------------------------------------
 Dim objShell
 
 Set objShell = CreateObject("WScript.Shell")
 'objShell.Run "cmd /C ""javac extractHtml.java & java extractHtml & notepad extractHtml.out & pause"""
 objShell.Run "cmd /C ""javac extractHtml.java & java extractHtml & notepad extractHtml.out"""
 Set objShell = Nothing
 
 '===============================================================================
 '       프로그램 명     : /ant_run.vbs
 '===============================================================================

DES 암복호화

• DES 암호화, 복호화 모듈

 public class UtilCrypto {
     public static Key desKey = null;
 
     public static Key getDesKey() {
         if (desKey == null) {
             desKey = makeDesKey();
         }
         return desKey;
     }
 
     public static void setDesKey(Key desKey) {
         UtilCrypto.desKey = desKey;
     }
     
     public static Key makeDesKey() {
         KeyGenerator generator = null;
 
         try {
             generator = KeyGenerator.getInstance("DES");
 //			generator = KeyGenerator.getInstance("TripleDES");
 //			generator = KeyGenerator.getInstance("AES");
             generator.init(new SecureRandom());
             return generator.generateKey();
         } catch (NoSuchAlgorithmException e) {
             e.printStackTrace();
         }
         return null;
     }
 
     public static String crypt(String algorithm, Integer cryptMode, Key key, String inpStr) {
         String rtStr = null;
         Cipher cipher = null;
         
         if ((inpStr == null) || (inpStr.length() == 0)) {
             return "";
         }
         
         try {
             if (algorithm.equals("DES")) {
                 cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
             } else if (algorithm.equals("TripleDES")) {
                 cipher = Cipher.getInstance("TripleDES/ECB/PKCS5Padding");
             } else if (algorithm.equals("RSA")) {
                 cipher = Cipher.getInstance("RSA");
             } else {
                 cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
             }
             
             if (cryptMode == Cipher.ENCRYPT_MODE) {
                 cipher.init(Cipher.ENCRYPT_MODE, key);
                 rtStr = Base64Encoder.encode(cipher.doFinal(inpStr.getBytes("UTF-8")));
             } else {
                 cipher.init(Cipher.DECRYPT_MODE, key);
                 rtStr = new String(cipher.doFinal(Base64Decoder.decodeToBytes(inpStr)), "UTF-8");
             }
         } catch (NoSuchAlgorithmException e) {
             e.printStackTrace();
         } catch (NoSuchPaddingException e) {
             e.printStackTrace();
         } catch (InvalidKeyException e) {
             e.printStackTrace();
         } catch (IllegalBlockSizeException e) {
             e.printStackTrace();
         } catch (BadPaddingException e) {
             e.printStackTrace();
         } catch (UnsupportedEncodingException e) {
             e.printStackTrace();
         }
         return rtStr;
     }
     
     public static String encryptDes(String plain) {
         return crypt("DES", Cipher.ENCRYPT_MODE, getDesKey(), plain);
     }
     
     public static String decryptDes(String security) {
         return crypt("DES", Cipher.DECRYPT_MODE, getDesKey(), security);
     }
 }

RSA 암복호화

 public class UtilCrypto {
     public static KeyPair rsaKey = null;
 
     public static KeyPair getRsaKeyPair() {
         if (rsaKey == null) {
             rsaKey = makeRsaKeyPair();
         }
         return rsaKey;
     }
     
     public static Key getRsaPublicKey() {
         if (rsaKey == null) {
             getRsaKeyPair();
         }
         return rsaKey.getPublic();
     }
 
     public static Key getRsaPrivateKey() {
         if (rsaKey == null) {
             getRsaKeyPair();
         }
         return rsaKey.getPrivate();
     }
     
     public static void setRsaKeyPair(KeyPair rsaKey) {
         UtilCrypto.rsaKey = rsaKey;
     }
     
     public static KeyPair makeRsaKeyPair() {
         KeyPairGenerator generator = null;
         
         try {
             generator = KeyPairGenerator.getInstance("RSA");
             generator.initialize(2048);						//--- keysize
             return generator.genKeyPair();
         } catch (NoSuchAlgorithmException e) {
             e.printStackTrace();
         }
         return null;
     }
 
     public static String encryptRsa(String plain) {
         return crypt("RSA", Cipher.ENCRYPT_MODE, getRsaPublicKey(), plain);
     }
     
     public static String decryptRsa(String security) {
         return crypt("RSA", Cipher.DECRYPT_MODE, getRsaPrivateKey(), security);
     }
 }

사용자 정의 프로그램

---

HTML에서 원하는 문자열 추출

• extractHtml.java : 여러 페이지로 작성된 HTML에서 원하는 문자열을 추출하는 프로그램, 필요시 수정하여 사용하세요.

 //==============================================================================
 //      프로그램 명     : extractHtml.java, Version 0.01
 //      프로그램 설명   : HTML에서 원하는 문자열을 추출
 //      작성자          : 산사랑
 //      작성일          : 2008.07.08 ~ 2008.07.08
 //----- [관리](History) ---------------------------------------------------------
 //      수정자          :
 //      수정일          :
 //      수정 내용       :
 //----- [Copyright](Copyright.md) ------------------------------------------------------------
 //      Copyright (c) 1995-2008 pnuskgh, All rights reserved.
 //==============================================================================
 import java.io.*;
 import java.net.*;
 
 class extractHtml
 {
     public static void main(String args[](.md)) 
     {
         int idx = 0, checkIdx = 0, cntRead = 0;
         URL url = null;
         String strUrl = "http://serverHost/main.php?catid=&skey=&page=";
         String inputLine = null;
         BufferedReader inp = null;
 
         BufferedWriter out = null;
         File outFile = null;
         String fileNameOut = "extractHtml.out";
         String delimiter = "|";
 
         try {
             outFile = new File(fileNameOut);
             if (outFile.exists()) {
                 outFile.delete();
             }
             out = new BufferedWriter(new FileWriter(outFile));
 
             for (idx = 1;idx <= 221;idx++) {
                 url = new URL(strUrl + idx);
                 inp = new BufferedReader(new InputStreamReader(url.openStream()));
                 while ((inputLine = inp.readLine()) != null) {
                     if (-1 < inputLine.indexOf("main.php?in=building_detail")) {
                         checkIdx = checkIdx + 1;
                         if (checkIdx == 1) {
                             out.write(idx + delimiter + ++cntRead + delimiter);
                             out.write(inputLine.substring(inputLine.lastIndexOf("'>") + 2, inputLine.indexOf("")) + delimiter);
                         }
                         if (checkIdx == 2) {
                             out.write(inputLine.substring(inputLine.lastIndexOf("'>") + 2, inputLine.indexOf("")) + delimiter);
                         }
                     }
                     if (-1 < inputLine.indexOf("/main.php?in=corp_detail&type=corp")) {
                         checkIdx = checkIdx + 1;
                         if (checkIdx == 5) {
                             out.write(inputLine.substring(inputLine.lastIndexOf("'>") + 2, inputLine.indexOf("")) + delimiter);
                             out.write("http://serverHost/main.php?id=" + inputLine.substring(inputLine.indexOf("id=") + 3, inputLine.indexOf("page=") - 1) + "\r\n");
                             checkIdx = 0;
                         } else {
                             out.write(inputLine.substring(inputLine.lastIndexOf("'>") + 2, inputLine.indexOf("")) +  delimiter);
                         }
                     }
                 }
                 inp.close();
             }
             out.flush();
             out.close();
         } catch (Exception e) {
             System.out.println(e);
         } finally {
             if (inp != null) {
                 try {
                     inp.close();
                 } catch (IOException e) {
                     e.printStackTrace();
                 }
             }
             inp = null;
 
             if (out != null) {
                 try {
                     out.close();
                 } catch (IOException e) {
                     e.printStackTrace();
                 }
             }
             out = null;
         }
     }
 }
 
 //==============================================================================
 //      프로그램 명     : extractHtml.java
 //==============================================================================

UUID 생성

• Universally Unique Identifier(또는 Globally Unique Identifier)의 종류

  • v1 : MAC address based
  • v2 : DCE Security based
  • v3 : Name based + MD5 hash
  • v4 : Random
  • v5 : Name based + SHA1 hash

• UUID의 구성

  • 128 bits (16 bytes) 숫자
  • 8-4-4-4-12 형태의 36개의 문자열

• Sample

 package kr.co.daou.common;
 
 import java.util.Random;
 import java.util.UUID;
 
 import org.safehaus.uuid.UUIDGenerator;
 
 public class GUID
 {
     private static Random rand = null;
     
     public static void main(String args[](.md)) {
         System.out.println("Unique ID Generation Test");
         
         for (int cnt = 0;cnt < 100;cnt ++) {
             System.out.println(getPrefixUUID("user"));
         }
     }
     
     public static String getPrefixUUID(String prefix)
     {
         return prefix + "." + getUUID1();
     }
     
     public static String getUUID() {
         return getUUID1();
     }
     
 
     //--- MAC address based, [uuid-3.2.jar (MIT License)](http://johannburkard.de/software/uuid/) 사용
     public static String getUUID1() {
         return (new com.eaio.uuid.UUID()).toString();
     }
 
     //--- Name based + MD5 hash, java.util.UUID 사용
     public static String getUUID3() {
         return getUUID3("Hello World!");
     }
 
     public static String getUUID3(String seed) {
         seed = seed + Long.toString(rand.nextLong());
         return UUID.nameUUIDFromBytes(seed.getBytes()).toString();
     }
 
     //--- Random, java.util.UUID 사용
     public static String getUUID4() {
         return UUID.randomUUID().toString();
     }
 
     //--- Random, [jug-lgpl-2.0.0.jar (GNU LGPL)](http://jug.safehaus.org/) 사용
     public static String getUUID4_1() {
         return UUIDGenerator.getInstance().generateRandomBasedUUID().toString();
     }
 
     //--- [jug-lgpl-2.0.0.jar (GNU LGPL)](http://jug.safehaus.org/) 사용
     public static String getUUID_jug() {
         return UUIDGenerator.getInstance().generateTimeBasedUUID().toString();
     }
 
     static {
         rand = new Random(System.currentTimeMillis());
     }
 }

• 참고 문헌
  • Universally unique identifier
  • Java UUID Generators
  • uuidgen
  • Java Uuid Generator (JUG)

Java 8

---

• Eclipse LUNA에서 Java 8을 공식적으로 지원

• Jigsaw

• 참고 문헌

• *Java 8 개선 사항 관련 글 모음, 2014.05

• *http://blog.fupfin.com/?p=27 [http://www.techempower.com/blog/2013/03/26/everything-about-java-8/]

• *[http://blog.fupfin.com/?p=27 [http://www.techempower.com/blog/2013/03/26/everything-about-java-8/ [http://www.oracle.com/kr/corporate/magazines/winter-tech2-1429486-ko.pdf]]](http://www.oracle.com/kr/corporate/magazines/winter-tech2-1429486-ko.pdf)

람다식 (Lambda Expression)

함수형 프로그램밍을 통해 멀티 코어 CPU 지원

람다식 형태

• (x, y) -> { x + y }
• (x, y) -> x + y
• x -> x + 5

 //--- 함수형 인터페이스 : 추상 메서드가 한개인 인터페이스
 @FunctionalInterface
 public interface funcArg {
 int methodOne(int a, int b);   
 }
 
 funcArg aa = (a, b) -> { return a + b }
 
 public void test(int one, int two, funcArg arg1) {
 arg1.methodOne(one, two);
 }
 test(1, 2, aa);

Stream (Java Collection API)

• Collection을 Pipe 형식으로 처리하는 함수형 API 지원
• Collection (List, Map, Set)을 Stream으로 처리
• java.util.stream

 List numbers = null;
 List strings = null;
 
 numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
 
 for (Integer number : numbers) {                       //--- 예전 방식
 System.out.println(number);
 }
 
 numbers.forEach(value -> System.out.println(value));   //--- 최신 방식 
 //--- numbers.forEach((Integer value) -> System.out.println(value));
 //--- numbers.forEach(System.out::println);
 
 strings = numbers.stream()
            .filter(v -> v > 4)
            .map(v -> new String("" + (v + 10)))
            .collect(Collectors.toList());
 strings.forEach(System.out::println);

스트림의 종류

• Stream<T>
• IntStream, LongStream, DoubleStream

병렬 처리

• 순차 처리 스트림
• *numbers.stream()
• *numbers.parallelStream().sequential()
• 병렬 처리 스트림
• *numbers.parallelStream()
• *numbers.stream().parallel()

스트림용 함수

• .forEach() : 각각에 대해서 처리
• .anyMatch() : 조건을 만족할 때 True 반환
• .filter() : True에 해당하는 데이터 반환
• .sorted() : 정렬 조건에 따라 정렬
• ~.collect(Collectors.toList()) : List 반환
• ~.findFirst() : 첫번째 데이터 반환
• .orElseThrow(() -> new Exception()) : 데이터가 없으면 Exception 발생

Nashorn

[[JavaScript|JavaScript]] 엔진으로 ECMAScript 5.1 (ECMA-262) 준수

Java 7의 invokedynamic 활용, Java 객체 호출 가능

javax.script (JSR 223) API 지원

Nashorn (나즈혼) 실행

• jjs 명령어
• ScriptManager

ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");
engine.eval("~");

문제 해결

---

• "java.lang.OutOfMemoryError: PermGen space" 오류가 발생할 경우 다음 옵션을 준다.

 -Xms512m
 -Xmx1024m
 -XX:PermSize=64M         //--- 해당 옵션
 -XX:MaxPermSize=128M     //--- 해당 옵션
 -verbose:gc
 -verbose:class

관련 자료

---

• [Java 8](Java 8.md)
• JDK
• HTML
• CSS

Java Decompiler

• JD-GUI : GUI 기반의 Java Decompiler (free for non-commercial use)
• JAD : 고전적인 Java Decompiler

참고 문헌

---

• Jdk15Han.chm

분류: 기술_자료실 Java 프로그램_언어

---