java - Javaでループを使用して変数名を作成しますか?

Question

初めてのポスター、長年の読者なので、私に優しくしてください:)

次のコードを参照して、会計年度の各月の開始と終了のタイムスタンプを生成してください。

int year = 2010;
// Financial year runs from Sept-Aug so earlyMonths are those where year = FY-1 and lateMonths are those where year = FY
int[] earlyMonths = {8, 9, 10, 11}; // Sept to Dec
int earlyYear = year -1;
for (int i : earlyMonths) {
    month = i;
    Calendar cal = Calendar.getInstance();
    cal.clear();
    cal.set(earlyYear,month,1,0,0,0);
    Long start = cal.getTimeInMillis();
    cal.clear();
    cal.set(earlyYear,month,1);
    lastDayofMonth = cal.getActualMaximum(GregorianCalendar.DAY_OF_MONTH);
    cal.set(earlyYear,month,lastDayofMonth,23,59,59);
    Long end = cal.getTimeInMillis();
}
int[] lateMonths = {0, 1, 2, 3, 4, 5, 6, 7}; // Jan to Aug
for (int i : lateMonths) {
    month = i;
    Calendar cal = Calendar.getInstance();
    cal.clear();
    cal.set(year,month,1,0,0,0);
    Long start = cal.getTimeInMillis();
    cal.clear();
    cal.set(year,month,1);
    lastDayofMonth = cal.getActualMaximum(GregorianCalendar.DAY_OF_MONTH);
    cal.set(year,month,lastDayofMonth,23,59,59);
    Long end = cal.getTimeInMillis();
}

ここまでは順調ですが、これらの結果を使用するには、これらのタイムスタンプを月ごとに名前を付けた変数に出力する必要があります (コードの後半の準備済みステートメントで使用します。たとえば、SeptStart = sometamp、SeptEnd = some timestamp など)。

各ループの結果に基づいて新しい変数を宣言できるかどうかはわかりません。何か案は？

Answer 1

Mapを使用しないのはなぜですか?

結局のところ、何らかの値の「コンテナ」を持ち、指定された名前でアドレス指定する必要があります。

したがって、「変数名」をキーに、「変数値」を値にします。

Sorted コレクションが必要だったので編集しました:

まず、 Map ではなくTreemapを使用します。

また、辞書式の順序を維持するために、月番号のパディング ゼロを左に正規化し、区切り文字として「begin」と「end」を使用します。

したがって、次のようになります。

01_begin
01_end
02_begin
...
10_begin
10_end
...

ツリーマップにアクセスすると、正しい順序で印刷されます。

Answer 2

変数名を生成する代わりにMap、キーが月名で、値がその月の値である を使用します。

Date septStart = some dateあなたができる代わりにstartDates.put("September", some date)

または、インデックスが月番号である配列に値を保存することもできます。startDates[8] = some date // 0-indexed!

Answer 3

変数を動的に宣言することはできません。タイムスタンプの 2 つの配列 (開始用と終了用) を宣言し、それらを埋めることをお勧めします。次に、名前付き変数の代わりにこれらの配列を使用するか、手動で変数を宣言して手動で設定します。

Calendar[] beginnings = new Calendar[12];
Calendar[] endings = new Calendar[12];

for (int i: earlyMontsh) {
  // Calc beginning ...
  beginnings[i] = cal;
  cal = Calendar.getInstance(); // Important, create new instance!
  // Calc ending ...
  endings[i] = cal;
}
// ... Same for second loop ...

Calendar janStart = beginnings[0];
Calendar janEnd = endings[0];
Calendar febStart = beginnigs[1];
Calendar febEnd = endings[1];
// .. And so on ...
Calendar decStart = beginnings[11];
Calendar decEnd = endings[11];

Answer 4

値を配列に格納すると、Calendar.Month 定数で値にアクセスできます。

import java.util.Calendar;
import java.util.GregorianCalendar;

public class Cal {

    Long[] start = new Long[12];
    Long[] end = new Long[12];

    private void init(int year) {
        for (int month = 0; month < 12; month++) {
            Calendar cal = Calendar.getInstance();
            cal.clear();
            cal.set(year, month, 1, 0, 0, 0);
            start[month] = cal.getTimeInMillis();
            cal.clear();
            cal.set(year, month, 1);
            int lastDayofMonth = cal
                    .getActualMaximum(GregorianCalendar.DAY_OF_MONTH);
            cal.set(year, month, lastDayofMonth, 23, 59, 59);
            end[month] = cal.getTimeInMillis();
        }
    }

    public static void main(String[] args) {
        Cal cal = new Cal();
        cal.init(2010);

        System.out.println( "start:" + cal.start[Calendar.JANUARY]+ " - " + cal.end[Calendar.JANUARY ]);
    }

}

Answer 5

マップは確かに良い解決策のようです:)私はjava / jsp（およびほとんどのプログラミング全般）に慣れていないので、これがどれほど簡単かを知りませんでした:)

次のコード:

// Financial year runs from Sept-Aug so earlyMonths are those where year = FY-1 and lateMonths are those where year = FY
HashMap hm = new HashMap();
int[] earlyMonths = {8, 9, 10, 11}; // Sept to Dec
int earlyYear = year -1;
for (int i : earlyMonths) {
    month = i;
    Calendar cal = Calendar.getInstance();
    cal.clear();
    cal.set(earlyYear,month,1,0,0,0);
    Long start = cal.getTimeInMillis();
    hm.put(month + "_start", new Long(start));
    cal.clear();
    cal.set(earlyYear,month,1);
    lastDayofMonth = cal.getActualMaximum(GregorianCalendar.DAY_OF_MONTH);
    cal.set(earlyYear,month,lastDayofMonth,23,59,59);
    Long end = cal.getTimeInMillis();
    hm.put(month + "_end", new Long(end));
}
int[] lateMonths = {0, 1, 2, 3, 4, 5, 6, 7}; // Jan to Aug
for (int i : lateMonths) {
    month = i;
    Calendar cal = Calendar.getInstance();
    cal.clear();
    cal.set(year,month,1,0,0,0);
    Long start = cal.getTimeInMillis();
    hm.put(month + "_start", new Long(start));
    cal.clear();
    cal.set(year,month,1);
    lastDayofMonth = cal.getActualMaximum(GregorianCalendar.DAY_OF_MONTH);
    cal.set(year,month,lastDayofMonth,23,59,59);
    Long end = cal.getTimeInMillis();
    hm.put(month + "_end", new Long(end));
}
Set set = hm.entrySet();
Iterator hmi = set.iterator();
while(hmi.hasNext()){
    Map.Entry me = (Map.Entry)hmi.next();
    out.println(me.getKey() + " : " + me.getValue() + "<br>");
}

次の出力が得られます。

4_end : 1275350399000
3_start : 1270080000000
8_end : 1254355199000
10_start : 1257033600000
1_start : 1264982400000
2_start : 1267401600000
8_start : 1251763200000
10_end : 1259625599000
0_start : 1262304000000
7_start : 1280620800000
0_end : 1264982399000
4_start : 1272672000000
5_start : 1275350400000
11_end : 1262303999000
5_end : 1277942399000
6_start : 1277942400000
9_start : 1254355200000
3_end : 1272671999000
2_end : 1270079999000
9_end : 1257033599000
11_start : 1259625600000
1_end : 1267401599000
7_end : 1283299199000
6_end : 1280620799000

なぜ、このように注文されたのか気になりました。機能に関しては重要ではありませんが、デバッグ目的でハッシュマップを注文することは可能ですか?

素晴らしい提案をありがとうございます:)

Answer 6

完了するために、完全なコードを投稿します。管理レポート用のデータベースから実稼働サーバーに関する可用性情報を引き出します。これは、私が JSP で行った中で最も複雑なことです:)

多くのことをよりエレガントに行うことができると確信しているので、お気軽にアドバイスしてください:) (明らかに、db パスワードなどは XXX アウトされています)

<%@page language="java" contentType="text/html"%>
<%@page import="java.util.*,java.sql.*,java.text.*"%>
<html>
<head>
    <title>KPI: FY10</title>
    <link rel="stylesheet" type="text/css" href="reports.css">
</head>
<%
// Example SQL "select count(timestamp) from jagel_hq_log where timestamp > 1270080000000 and timestamp < 1272671999000 and kpi_id = 9"

/* ------------- START CONFIGURABLE VARIABLES -------------*/

int year = 2010;
boolean leapYear = false;
String db_user = "XXXX";
String db_pass = "XXXX";

// Special Case of Leap Years
int febMins;
if(leapYear=true) {
    febMins = 41760;
    }
    else {
    febMins = 44640;    
    }

int yearMins;
if(leapYear=true) {
    yearMins = 527040;
    }
    else {
    yearMins = 525600;
    }
int minsYear = yearMins;

// minutes in each month
int minsJan = 44640;
int minsFeb = febMins;
int minsMar = 44640;
float minsApr = 43200;
int minsMay = 44640;
int minsJun = 43200;
int minsJul = 44640;
int minsAug = 44640;
int minsSep = 43200;
int minsOct = 44640;
int minsNov = 43200;
int minsDec = 44640;

String maxAvail = "#CDEB8B";
String medAvail = "#FFFF88";
String minAvail = "#FDE8D7";
String colour;


/* ------------- END CONFIGURABLE VARIABLES -------------*/

/* Initialise Variables */
int month = 0;
int lastDayofMonth;
int totalMins = 0;
float mins_down = 0;
float avail = 0;
DecimalFormat round = new DecimalFormat("###.###");
Long startTime;
Long endTime;

// Connect to DB
DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
String connString="jdbc:oracle:thin:@XXXXXXXX.XXXXX.com:XXXX:XXXXXX";
Connection conn = DriverManager.getConnection(connString,db_user,db_pass);

/* Get months of year as 'to' and 'from' timestamps */
// Financial year runs from Sept-Aug so earlyMonths are those where 'year = FY-1' and lateMonths are those where 'year = FY'
HashMap hm = new HashMap();
int[] earlyMonths = {8, 9, 10, 11}; // Sept to Dec
int earlyYear = year -1;
for (int i : earlyMonths) {
    month = i;
    Calendar cal = Calendar.getInstance();
    cal.clear();
    cal.set(earlyYear,month,1,0,0,0);
    Long start = cal.getTimeInMillis();
    hm.put(month + "_start", new Long(start));
    cal.clear();
    cal.set(earlyYear,month,1);
    lastDayofMonth = cal.getActualMaximum(GregorianCalendar.DAY_OF_MONTH);
    cal.set(earlyYear,month,lastDayofMonth,23,59,59);
    Long end = cal.getTimeInMillis();
    hm.put(month + "_end", new Long(end));
}
int[] lateMonths = {0, 1, 2, 3, 4, 5, 6, 7}; // Jan to Aug
for (int i : lateMonths) {
    month = i;
    Calendar cal = Calendar.getInstance();
    cal.clear();
    cal.set(year,month,1,0,0,0);
    Long start = cal.getTimeInMillis();
    hm.put(month + "_start", new Long(start));
    cal.clear();
    cal.set(year,month,1);
    lastDayofMonth = cal.getActualMaximum(GregorianCalendar.DAY_OF_MONTH);
    cal.set(year,month,lastDayofMonth,23,59,59);
    Long end = cal.getTimeInMillis();
    hm.put(month + "_end", new Long(end));
}
%>

<!-- Header -->
<a href="index.jsp"><-- Back to Index</a><br>
<div align="center">
<h2>IITP Availability Report</h2>
<%
Calendar c = Calendar.getInstance();
out.println("Report Generated: " + c.getTime() + " and accurate up to (and including) yesterday");
%>
</div>

<!-- Start Table -->
<table class="mar">
<tr>
    <th class="header">KPI Name</th>
    <th class="header">Description</th>
    <th class="header" colspan="2">Sep <% out.println( year - 1 ); %></th>  
    <th class="header" colspan="2">Oct <% out.println( year - 1 ); %></th>  
    <th class="header" colspan="2">Nov <% out.println( year - 1 ); %></th>
    <th class="header" colspan="2">Dec <% out.println( year - 1 ); %></th>
    <th class="header" colspan="2">Jan <% out.println( year ); %></th>
    <th class="header" colspan="2">Feb <% out.println( year ); %></th>
    <th class="header" colspan="2">Mar <% out.println( year ); %></th>
    <th class="header" colspan="2">Apr <% out.println( year ); %></th>
    <th class="header" colspan="2">May <% out.println( year ); %></th>
    <th class="header" colspan="2">Jun <% out.println( year ); %></th>
    <th class="header" colspan="2">Jul <% out.println( year ); %></th>
    <th class="header" colspan="2">Aug <% out.println( year ); %></th>
    <th class="header" colspan="2">Avg <% out.println( year ); %></th>
</tr>
<tr>
    <th class="top">&nbsp</th>
    <th class="top">&nbsp</th>
    <th class="top">Mins Down</th>
    <th class="top">% Avail</th>
    <th class="top">Mins Down</th>
    <th class="top">% Avail</th>
    <th class="top">Mins Down</th>
    <th class="top">% Avail</th>
    <th class="top">Mins Down</th>
    <th class="top">% Avail</th>
    <th class="top">Mins Down</th>
    <th class="top">% Avail</th>
    <th class="top">Mins Down</th>
    <th class="top">% Avail</th>
    <th class="top">Mins Down</th>
    <th class="top">% Avail</th>
    <th class="top">Mins Down</th>
    <th class="top">% Avail</th>
    <th class="top">Mins Down</th>
    <th class="top">% Avail</th>
    <th class="top">Mins Down</th>
    <th class="top">% Avail</th>
    <th class="top">Mins Down</th>
    <th class="top">% Avail</th>
    <th class="top">Mins Down</th>
    <th class="top">% Avail</th>
    <th class="top">Mins Down</th>
    <th class="top">% Avail</th>
</tr>
<%
// Get all KPI_ID's
Statement stmt = conn.createStatement();
ResultSet rs_id = stmt.executeQuery("select distinct (KPI_ID) from JAGEL_KPI_SPECS order by KPI_ID");

// initialise Result Set
ResultSet rs_minsDown;

while (rs_id.next()){
    int id = rs_id.getInt("KPI_ID");

    // Get the kpi name and description from db
    PreparedStatement ps_names = conn.prepareStatement("select KPI_ID, KPI_GROUP_NAME, DESCRIPTION from JAGEL_KPI_SPECS where KPI_ID = " + id);
    ResultSet rs_names = ps_names.executeQuery();
    while (rs_names.next()) {
        out.println("<tr><td>" + rs_names.getString("KPI_GROUP_NAME") + "</td><td>" + rs_names.getString("DESCRIPTION") + "</td>");
    }
    rs_names.close();

    // get the number of minutes down for each month and availability %
    PreparedStatement ps_minsDown = conn.prepareStatement("select count(timestamp) from jagel_hq_log where timestamp > ? and timestamp < ? and kpi_id = " + id);
    //September
    startTime = (Long) hm.get("8_start");
    endTime = (Long) hm.get("8_end");
    ps_minsDown.setLong(1,startTime);
    ps_minsDown.setLong(2,endTime);
    rs_minsDown = ps_minsDown.executeQuery();
    rs_minsDown.next();
    mins_down = rs_minsDown.getInt("COUNT(TIMESTAMP)");
    avail = 100-(mins_down/minsSep*100);
    if(avail < 99.98) {
        colour=minAvail;
        }
    else if(avail < 100){
        colour=medAvail;
        }
    else {
        colour=maxAvail;
    }
    out.println("<td bgcolor=" + colour + ">" + mins_down + "</td><td bgcolor=" + colour + ">" + round.format(avail) + "%");
    rs_minsDown.close();
    //October
    startTime = (Long) hm.get("9_start");
    endTime = (Long) hm.get("9_end");
    ps_minsDown.setLong(1,startTime);
    ps_minsDown.setLong(2,endTime);
    rs_minsDown = ps_minsDown.executeQuery();
    rs_minsDown.next();
    mins_down = rs_minsDown.getInt("COUNT(TIMESTAMP)");
    avail = 100-(mins_down/minsOct*100);
    if(avail < 99.98) {
        colour=minAvail;
        }
    else if(avail < 100){
        colour=medAvail;
        }
    else {
        colour=maxAvail;
    }
    out.println("<td bgcolor=" + colour + ">" + mins_down + "</td><td bgcolor=" + colour + ">" + round.format(avail) + "%");
    rs_minsDown.close();
    //November
    startTime = (Long) hm.get("10_start");
    endTime = (Long) hm.get("10_end");
    ps_minsDown.setLong(1,startTime);
    ps_minsDown.setLong(2,endTime);
    rs_minsDown = ps_minsDown.executeQuery();
    rs_minsDown.next();
    mins_down = rs_minsDown.getInt("COUNT(TIMESTAMP)");
    avail = 100-(mins_down/minsNov*100);
    if(avail < 99.98) {
        colour=minAvail;
        }
    else if(avail < 100){
        colour=medAvail;
        }
    else {
        colour=maxAvail;
    }   
    out.println("<td bgcolor=" + colour + ">" + mins_down + "</td><td bgcolor=" + colour + ">" + round.format(avail) + "%");
    rs_minsDown.close();
    //December
    startTime = (Long) hm.get("11_start");
    endTime = (Long) hm.get("11_end");
    ps_minsDown.setLong(1,startTime);
    ps_minsDown.setLong(2,endTime);
    rs_minsDown = ps_minsDown.executeQuery();
    rs_minsDown.next();
    mins_down = rs_minsDown.getInt("COUNT(TIMESTAMP)");
    avail = 100-(mins_down/minsDec*100);
    if(avail < 99.98) {
        colour=minAvail;
        }
    else if(avail < 100){
        colour=medAvail;
        }
    else {
        colour=maxAvail;
    }
    out.println("<td bgcolor=" + colour + ">" + mins_down + "</td><td bgcolor=" + colour + ">" + round.format(avail) + "%");
    rs_minsDown.close();
    //January
    startTime = (Long) hm.get("0_start");
    endTime = (Long) hm.get("0_end");
    ps_minsDown.setLong(1,startTime);
    ps_minsDown.setLong(2,endTime);
    rs_minsDown = ps_minsDown.executeQuery();
    rs_minsDown.next();
    mins_down = rs_minsDown.getInt("COUNT(TIMESTAMP)");
    avail = 100-(mins_down/minsJan*100);
    if(avail < 99.98) {
        colour=minAvail;
        }
    else if(avail < 100){
        colour=medAvail;
        }
    else {
        colour=maxAvail;
    }
    out.println("<td bgcolor=" + colour + ">" + mins_down + "</td><td bgcolor=" + colour + ">" + round.format(avail) + "%");
    rs_minsDown.close();
    //February
    startTime = (Long) hm.get("1_start");
    endTime = (Long) hm.get("1_end");
    ps_minsDown.setLong(1,startTime);
    ps_minsDown.setLong(2,endTime);
    rs_minsDown = ps_minsDown.executeQuery();
    rs_minsDown.next();
    mins_down = rs_minsDown.getInt("COUNT(TIMESTAMP)");
    avail = 100-(mins_down/minsFeb*100);
    if(avail < 99.98) {
        colour=minAvail;
        }
    else if(avail < 100){
        colour=medAvail;
        }
    else {
        colour=maxAvail;
    }
    out.println("<td bgcolor=" + colour + ">" + mins_down + "</td><td bgcolor=" + colour + ">" + round.format(avail) + "%");
    rs_minsDown.close();
    //March
    startTime = (Long) hm.get("2_start");
    endTime = (Long) hm.get("2_end");
    ps_minsDown.setLong(1,startTime);
    ps_minsDown.setLong(2,endTime);
    rs_minsDown = ps_minsDown.executeQuery();
    rs_minsDown.next();
    mins_down = rs_minsDown.getInt("COUNT(TIMESTAMP)");
    avail = 100-(mins_down/minsMar*100);
    if(avail < 99.98) {
        colour=minAvail;
        }
    else if(avail < 100){
        colour=medAvail;
        }
    else {
        colour=maxAvail;
    }
    out.println("<td bgcolor=" + colour + ">" + mins_down + "</td><td bgcolor=" + colour + ">" + round.format(avail) + "%");
    rs_minsDown.close();
    //April
    startTime = (Long) hm.get("3_start");
    endTime = (Long) hm.get("3_end");
    ps_minsDown.setLong(1,startTime);
    ps_minsDown.setLong(2,endTime);
    rs_minsDown = ps_minsDown.executeQuery();
    rs_minsDown.next();
    mins_down = rs_minsDown.getInt("COUNT(TIMESTAMP)");
    avail = 100-(mins_down/minsApr*100);
    if(avail < 99.98) {
        colour=minAvail;
        }
    else if(avail < 100){
        colour=medAvail;
        }
    else {
        colour=maxAvail;
    }
    out.println("<td bgcolor=" + colour + ">" + mins_down + "</td><td bgcolor=" + colour + ">" + round.format(avail) + "%");
    rs_minsDown.close();
    //May
    startTime = (Long) hm.get("4_start");
    endTime = (Long) hm.get("4_end");
    ps_minsDown.setLong(1,startTime);
    ps_minsDown.setLong(2,endTime);
    rs_minsDown = ps_minsDown.executeQuery();
    rs_minsDown.next();
    mins_down = rs_minsDown.getInt("COUNT(TIMESTAMP)");
    avail = 100-(mins_down/minsMay*100);
    if(avail < 99.98) {
        colour=minAvail;
        }
    else if(avail < 100){
        colour=medAvail;
        }
    else {
        colour=maxAvail;
    }
    out.println("<td bgcolor=" + colour + ">" + mins_down + "</td><td bgcolor=" + colour + ">" + round.format(avail) + "%");
    rs_minsDown.close();
    //June
    startTime = (Long) hm.get("5_start");
    endTime = (Long) hm.get("5_end");
    ps_minsDown.setLong(1,startTime);
    ps_minsDown.setLong(2,endTime);
    rs_minsDown = ps_minsDown.executeQuery();
    rs_minsDown.next();
    mins_down = rs_minsDown.getInt("COUNT(TIMESTAMP)");
    avail = 100-(mins_down/minsMay*100);
    if(avail < 99.98) {
        colour=minAvail;
        }
    else if(avail < 100){
        colour=medAvail;
        }
    else {
        colour=maxAvail;
    }
    out.println("<td bgcolor=" + colour + ">" + mins_down + "</td><td bgcolor=" + colour + ">" + round.format(avail) + "%");
    rs_minsDown.close();
    //July
    startTime = (Long) hm.get("6_start");
    endTime = (Long) hm.get("6_end");
    ps_minsDown.setLong(1,startTime);
    ps_minsDown.setLong(2,endTime);
    rs_minsDown = ps_minsDown.executeQuery();
    rs_minsDown.next();
    mins_down = rs_minsDown.getInt("COUNT(TIMESTAMP)");
    avail = 100-(mins_down/minsJul*100);
    if(avail < 99.98) {
        colour=minAvail;
        }
    else if(avail < 100){
        colour=medAvail;
        }
    else {
        colour=maxAvail;
    }
    out.println("<td bgcolor=" + colour + ">" + mins_down + "</td><td bgcolor=" + colour + ">" + round.format(avail) + "%");
    rs_minsDown.close();
    //August
    startTime = (Long) hm.get("7_start");
    endTime = (Long) hm.get("7_end");
    ps_minsDown.setLong(1,startTime);
    ps_minsDown.setLong(2,endTime);
    rs_minsDown = ps_minsDown.executeQuery();
    rs_minsDown.next();
    mins_down = rs_minsDown.getInt("COUNT(TIMESTAMP)");
    avail = 100-(mins_down/minsAug*100);
    if(avail < 99.98) {
        colour=minAvail;
        }
    else if(avail < 100){
        colour=medAvail;
        }
    else {
        colour=maxAvail;
    }
    out.println("<td bgcolor=" + colour + ">" + mins_down + "</td><td bgcolor=" + colour + ">" + round.format(avail) + "%");
    rs_minsDown.close();
    //YEAR
    startTime = (Long) hm.get("8_start");
    endTime = (Long) hm.get("7_end");
    ps_minsDown.setLong(1,startTime);
    ps_minsDown.setLong(2,endTime);
    rs_minsDown = ps_minsDown.executeQuery();
    rs_minsDown.next();
    mins_down = rs_minsDown.getInt("COUNT(TIMESTAMP)");
    avail = 100-(mins_down/minsYear*100);
    if(avail < 99.98) {
        colour=minAvail;
        }
    else if(avail < 100){
        colour=medAvail;
        }
    else {
        colour=maxAvail;
    }
    out.println("<td bgcolor=" + colour + ">" + mins_down + "</td><td bgcolor=" + colour + ">" + round.format(avail) + "%");
    rs_minsDown.close();
}
// close remaining result set and connection
rs_id.close();
conn.close();
%>
</table>
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