Java Basic
概要 (Java 2 プラットフォーム SE v1.4.0)
宣言 | String str = "hello"; | |
String str = new String("hello"); | ||
配列定義 | float fltAbc[] = {0,0,0}; | |
float ltAbc[] = new float[3]; String str[] = new String[3]; |
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String str[] = abc(); for (int i = 0 ; i < str.length ; i++) { System.out.println("str=" + str[i] + " i=" + i); } public static String[] abc() { String strabc[] = {"a","b","c"}; return strabc; } |
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String p_info [] = {"エラー(あ="+p_xxxx1+" い="+p_xxxx2+")"}; p_info [0] = "エラー(あ="+p_xxxx1+" い="+p_xxxx2+")"; ??? String p_error [] = {"あ","い","う"}; error(p_error[0]); error(p_error[1]); error(p_error[2]); |
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String str[]; str = new String[3]; |
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int ix1 = 0; String strAbc[] = {"a","b","c"}; ix1 = 1; System.out.println("strAbc 1:" + strAbc[ix1]); //strAbc 1:b System.out.println("strAbc 2:" + strAbc[ix1+1]); //strAbc 1:c System.out.println("strAbc 3:" + strAbc[2-1]); //strAbc 1:b |
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キャスト | intWork = (int)100 ; | |
型変換
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float flt1 = Float.parseFloat(str1.toString()); | String -> float |
int int1 = Integer.parseInt(str1.toString()); | String -> int | |
pstmt.setBigDecimal(1,new BigDecimal("1")); | String -> BigDecimal | |
String str1 = String.valueOf(int1); | int -> String | |
String str1 = String.valueOf(flt1); | float -> String | |
t_Upd.setsnd(snd.toString()); | BigDecimal -> String | |
t_Upd.setsnd(String.valueOf(snd)); | BigDecimal -> String | |
flosnd = snd.floatValue(); | BigDecimal -> float | |
int in1 = integer1.intValue(); | Integer -> int | |
float snd = (float)intcnt; | int -> float | |
BigDecimal | add(BigDecimal val) 値が (this + val) subtract(BigDecimal val) 値が (this - val) multiply(BigDecimal val) 値が (this * val) divide(BigDecimal val,int scale,int roundingMode) 値が (this / val) ROUND_UP, ROUND_DOWN, ROUND_CEILING, ROUND_FLOOR, ROUND_HALF_UP, ROUND_HALF_DOWN, ROUND_HALF_EVEN, ROUND_UNNECESSARY ynd = ynd.add(t_Sel.getZND(0)); ynd = ynd.subtract(snd); bihm = bighm.divide(bignin,2,BigDecimal.ROUND_HALF_UP) if (nhm.add(nhm).compareTo(new BigDecimal("7.0")) >= 0) { hnd = hnd.add(new BigDecimal("1.0")); } if (hm.compareTo(new BigDecimal("0.0")) == 0) { } BigDecimal en = new BigDecimal(0); BigDecimal zan = new BigDecimal(0); zan = zan.add(en); DecimalFormat formatter0 = new DecimalFormat ("0.00"); BigDecimal biga = new BigDecimal(11); BigDecimal bigb = new BigDecimal(1.00); biga = biga.subtract(bigb); System.out.println("="+formatter0.format(biga)); //=10.00 biga = new BigDecimal(0); bigb = new BigDecimal(0.0); if (biga.compareTo(bigb) == 0) { System.out.println("=="); // == } else { System.out.println("<>"); } 0.1を100回加算誤差 BigDecimal 10.0000000000000005551115123125782702118158340454101562500 float 10.000002 double 9.99999999999998 0.1を1000回加算誤差 BigDecimal 100.0000000000000055511151231257827021181583404541015625000 float 99.99905 double 99.9999999999986 |
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比較 | if (str1.toString().trim().equals("")) {} | |
if (Integer1.equals(Integer2)) {} | ||
if ( "2".equals(str1) ) { | ||
if (str1 == null) {} | ||
if (str1 != null) {} | ||
if (!chk("a")) {} | boolean chk(String kbn) | |
if (str1.compareTo(str2) < 0) {} ← 推奨 if (str1.compareTo(str2) = 0) {} if (str1.compareTo(str2) > 0) {} |
str1<str2 → 0 より小さい str1=str2 → 0 str1>str2 → 0より大きい |
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if (kbn.equals("1")) { } else if (kbn.equals("2")) { } else if (kbn.equals("3")) { } |
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分岐 | switch(border) { case 1: style.setBorderRight(HSSFCellStyle.BORDER_DASH_DOT); style.setRightBorderColor(HSSFCellStyle.BLACK); break ; default: } |
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長さ | if (str1.toString().length() == 1) {} | |
String aaa = "漢字123456"; System.out.println("a:" + aaa.getBytes().length); System.out.println("b:" + aaa.length()); |
a:10 b:8 |
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文字操作 | if (str1.substring(0,1).toString().equals("1")) {} | 先頭から1桁 |
"hamburger".substring(4, 8) では "urge" が返される | ||
StringTokenizer st = new StringTokenizer("this is a
test"); while (st.hasMoreTokens()) { println(st.nextToken()); } |
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"smiles".substring(1, 5) では "mile" が返される | ||
String str = "1,Java00"; byte [] bytes = str.getBytes(); System.out.println("1:" + new String(bytes,0,1)); //1:1 System.out.println("2:" + new String(bytes,1,1)); //2:, System.out.println("3:" + new String(bytes,2,8)); //3:Java System.out.println("4:" + new String(bytes,10,2)); //4:00 |
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row.createCell((short)8).setCellValue(symd.substring(0,4)); //日付 row.createCell((short)9).setCellValue(symd.substring(4,6)); //日付 row.createCell((short)10).setCellValue(symd.substring(6,8)); //日付 |
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連結 | concat(String str)
指定された文字列をこの文字列の最後に連結します。 return ans.concat("11111"); |
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改行 | strText = strText + "\n"; | |
パス | c:\\test\\test.txt | |
置換 | String strman1 = "U" + aline.substring(IXS[5],IXE[5]).replace(' ','0'); a.replace(' ',' ') |
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フォーマット | SimpleDateFormat formatter = new SimpleDateFormat ("yyyyMMddHHmmss"); |
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DecimalFormat formatter0 = new DecimalFormat ("0000000"); | ||
使用例 | java.util.Date currenttime = new java.util.Date(); String stdate = formatter.format(currenttime).substring(0,8); //日 String sttime = formatter.format(currenttime).substring(8,14); //時間 formatter0.format(inputcount) |
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TimeStamp | java.util.Date currenttime = new java.util.Date(); java.sql.Timestamp timestampvalue = new java.sql.Timestamp(currenttime.getTime()); pstmt.setTimestamp(4,timestampvalue); |
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結合 | "aaa" + "bbb" | |
StringBuffer textfile = new StringBuffer(""); textfile.append("aaa"); textfile.append("bbb"); |
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ループ | for (int i = 0 ; i < 2 ; i++) { } |
2回 break ラベル; continue ラベル; |
String wbk = strtbl[0]; while (strtbl[cnt].equals(wbk)) { //偽の時抜ける } String str[] = new String[10]; str[0] = "0"; str[1] = "1"; str[2] = "2"; int i = 0 ; while (str[i]!=null) { i = i + 1; System.out.println("i-cnt="+i); } System.out.println("i-end="+i); //i-cnt=1 //i-cnt=2 //i-cnt=3 //i-end=3 |
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int cnt = 0; String strtbl[] = {"111","111","222","333","333","333","444"}; String wbk = strtbl[0]; for (int int1 = 0 ; int1 < 7 ; int1++) { if (int1 == 0) { wbk = strtbl[0]; } System.out.println("wbk="+wbk); if (strtbl[int1].equals(wbk)) { cnt = cnt + 1 ; } else { wbk = strtbl[int1]; } } System.out.println("wbk="+wbk); System.out.println("cnt="+cnt); |
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条件 | && -> and , || -> or | |
引数 | if (args[0].endsWith("xml")) { System.out.println("*** test1 ***"); } else { System.out.println("*** test2 ***"); } |
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public static void main(String[] args) { System.out.println("args0:" + args[0]); System.out.println("args1:" + args[1]); } C:\j2sdk1.4.0_01\bin\java test "AAA" "BBB" |
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文字コード | JISAutoDetect Shift-JIS、EUC-JP、ISO 2022 JPの検出および変換(Unicode変換のみ) SJIS Shift-JIS、日本語 MS932 Windows日本語 Cp943C IBM OS/2日本語拡張 UTF8 8ビットUnicode変換形式 |
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//rs_z010.getString("ADDRESS1") -> 大浜西町2−2 String text5 = new String(rs_z010.getString("ADDRESS1").getBytes("SJIS")); System.out.println("text5=" + text5); //text5=大浜西町2−2 System.out.println( new String(rs_z010.getString("NM").getBytes("SJIS"))); System.out.println( new String(rs_z010.getString("NM").getBytes("Cp943C"))); |
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//出力ファイル targetfile = new File(backfile); pwout = new PrintWriter( new BufferedWriter( new OutputStreamWriter( new FileOutputStream(targetfile.getPath(),true),"Cp943C") ),false ); |
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禁断? | System.exit(0); | |
Exception | Exception appErr = new Exception(); throw appErr; } catch(Exception e) { cat.fatal(e); } finally { } |
catch (Throwable e) |
heep | java.lang.Runtime.getRuntime().totalMemory(); java.lang.Runtime.getRuntime().freeMemory(); long tota = Runtime.getRuntime().totalMemory(); long free = Runtime.getRuntime().freeMemory(); System.out.println("heapsize," total_First - free); |
class -mx xxxxxxx |
excel起動 | String os = System.getProperty( "os.name" ); Runtime runtime = Runtime.getRuntime(); System.out.println("os:" + os); if( os.equals( "Windows 98" ) || os.equals( "Windows Me" ) ) { Process proc = runtime.exec( "start test.xls /e"); proc.waitFor(); } else { Process proc = runtime.exec( "cmd /C start /MIN test.xls /e" ); proc.waitFor(); } |
←確認済 ←確認済 Windows2000 |
システム | strTIME = String.valueOf( System.currentTimeMillis()); | 時間 |
gc | java.lang.System.gc(); | |
" | \"->" | |
sleep | public static void main(String[] args) { SimpleDateFormat formatter = new SimpleDateFormat ("yyyyMMddHHmmss"); java.util.Date currenttime = new java.util.Date(); currenttime = new java.util.Date(); String sttime = formatter.format(currenttime).substring(8,14); System.out.println("sttime1 = "+sttime); sleep(1000); //1秒お待ち currenttime = new java.util.Date(); sttime = formatter.format(currenttime).substring(8,14); System.out.println("sttime2 = "+sttime); } static void sleep(int time) { try { Thread.sleep(time); } catch (InterruptedException e) { } } |
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try catch | try { //} catch (Throwable theException) { } catch (Throwable e) { System.out.println("abend=" + e); } finally { xxx.closeResultSet(); } |
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try finally | public boolean del(String strcd) { Del01DBBean Del01 = new Del01DBBean(); try { Del01.setCd(strcd); Del01.execute(); return(true); } catch (Throwable theException) { return(false); } finally { Del01.closeResultSet(); } } |
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Sample | public xxxBean(int index) { strCheck = new String[index]; } protected String strKBN = ""; public String getKbn() {return(strKBN);} public void setKbn(String value) {strKBN = value;} protected String strCheck[]; public String getCheck(int index) {return(strCheck[index]);} public void setCheck(String value, int index) {strCheck[index] = value;} public String cKBN(String strKBN[]) { if (strKBN == null){ return(""); } if (strKBN[0].equals("on")){ return("checked"); } return("0"); } ---------------------------------------------------------------- B800.setKbn(new String(getParameter(request, "KBN", true, true, true, null))); xxx.setCheck(xxx.cKBN(request.getParameterValues("CHECK" + String.valueOf(i))),i); String wktest[] = request.getParameterValues("TEST"); xxx.setTest(test[index],index); ---------------------------------------------------------------- <INPUT <%= xxx.getChe(i) %> type="checkbox" name="CHECK<%=xxx.getIx(i) %>"> ---------------------------------------------------------------- int p_rscnt = 0; int p_pgcnt = 0; int p_max = 10; p_rscnt = rs.getNumResult(); p_pgcnt = (rscnt + p_max - 1) / p_max //最終ページ Integer.toString(p_pgcnt); |
Calendarクラスの持つ主なフィールド | |
フィールド名 |
説 明 |
DATE | 日付を整数で示す |
DAY_OF_MONTH | DATEと同じ内容を示す |
DAY_OF_WEEK | 曜日を示す |
DAY_OF_WEEK_IN_MONTH | 現在の月の何度目の曜日かを示す |
DAY_OF_YEAR | 現在の年の何日目かを示す |
HOUR | 12時間制の時刻を示す |
HOUR_OF_DAY | 24時間制の時刻を示す |
MILLISECOND | 現在の時刻のうち、ミリ秒の部分を示す |
MINUTE | 現在の時刻のうち、分の部分を示す |
MONTH | 月を示す(1月が0、2月が1・・・となる) |
SECOND | 現在の時刻のうち、秒の部分を示す |
WEEK_OF_MONTH | 現在の月の何週目かを示す |
WEEK_OF_YEAR | 現在の年の何週目かを示す |
YEAR | 年を示す |