java - 需要帮助 'combining' Java ArrayList 中存在部分重复项

Question

        public class Pair{

             public String key;
             public String value;
             public String amount;

             public Pair(String key, String value, String amount){
                  this.key = key;
                  this.value = value;
                  this.amount = amount;
             }

             public Pair(String key, String value){
                  this.key = key;
                  this.value = value;
             }

             public String getKey(){
                  return key;
             }
             public String getValue(){
                  return value;
             }
             public String getAmount(){
                  return amount;
             }
             public void setAmount(String amount){
                  this.amount =  amount;
             }
        }

<小时/>

        List<Pair> pairs = new ArrayList<Pair>();
        List<Pair> duplicates = new ArrayList<Pair>();
        List<Pair> duplicatesWithAmounts = new ArrayList<Pair>();

        for (String line:lines){

            String[] lineparts = line.split(",");

            if ( line.startsWith("Date") || lineparts[3].equals("0.00") || lineparts[3].equals("-0.00") || lineparts[3].equals("000") || lineparts[3].equals("0000") || lineparts[3].equals("00000") ) {
                continue;
            }

            String description = lineparts[4];
            String acct = lineparts[2];
            String amt = lineparts[3];

            Pair pair = new Pair(description, acct);
            Pair pair2 = new Pair(description, acct, amt);

                if(!pairs.isEmpty() && pairs.contains(pair)) {
                    duplicates.add(pair);
                    duplicatesWithAmounts.add(pair2);
                }

            pairs.add(pair);

        }


    for (String linefromFile:lines){

        String[] lineparts = linefromFile.split(",");

        String description = lineparts[4];
        String acct = lineparts[2];
        String amt = lineparts[3];

        Pair pair = new Pair(description, acct);
        Pair pair2 = new Pair(description, acct, amt);

        if(!duplicates.contains(pair)){
            continue;
        }
        duplicates.remove(pair);

       //Here is where I'm lost....

    }

注意:金额目前是字符串，它们相加时将传递给新的 BigDecimal，但尚未到达该位置

注2:“lines”是 CSV 字符串的数组列表

我需要在注释所在的地方做的事情(说这里是我迷失的地方......)，是根据它们的键和值将重复项合并到duplicatesWithAmounts中，并且对于键和值匹配的每个对象，将金额相加(可能有负数，但如果我们使用BigDecimal，那应该不重要)。因此，如果我有 3 行具有相同的键和值(无论金额不同)，我将以 1 行包含该键和值以及 3 个金额的总和结束。

可能存在重复的示例数据的想法:

“0001，测试1，147.00”

“0001，测试1，129.00”

“0001，测试1，-17.00”

“0002，测试2，7.00”

“0002，测试2，-7.00”

“0003，测试3，30.00”

“0003，测试3，-12.00”

我想结束:

“0001，测试1，259.00”

“0002，测试2，0.00”

“0003，测试3，18.00”

非常感谢任何帮助，我是一名初级开发人员，一直在努力应对这个时间敏感的项目。我确信从一开始就有更好的方法来做到这一点，没有我的 Pair 类等，也没有我的对数组，所以如果有人向我展示也很好。但我也很想知道如何从我目前拥有的东西中获得我需要的东西，以用于学习目的。这些都在“进行交易行”部分内。

<小时/>

好吧，我尝试了斯特凡的方法，虽然我以为我已经弄清楚了一切。我正在正确输出中的行数，没有重复，但是每行的所有行数似乎都非常大。比应有的大得多。

package src;

import java.math.BigDecimal;

public class WDETotalsByDescription{

public String start;
public String end;
public String account;
public BigDecimal amount = new BigDecimal(0);

public String getStart() {
    return start;
}

public void setStart(String start) {
    this.start = start;
}

public String getEnd() {
    return end;
}

public void setEnd(String end) {
    this.end = end;
}

public String getAccount() {
    return account;
}

public void setAccount(String account) {
    this.account = account;
}

public BigDecimal getAmount() {
    return amount;
}

public void setAmount(BigDecimal amount) {
    this.amount = amount;
}

public WDETotalsByDescription(){

}

}

<小时/>

public static ArrayList<String> makeWestPacDirectEntry(ArrayList<String> lines, ParametersParser pp){

    ArrayList<String> fileLines = new ArrayList<String>();

//制作头记录

    fileLines.add("0 " +
            formatField(pp.getBank(), 21, RIGHT_JUSTIFIED, BLANK_FILLED) +
            "       " +
            formatField(pp.getNameOfUser(), 26, LEFT_JUSTIFIED, BLANK_FILLED) +
            formatField(pp.getNumberOfUser(),6,LEFT_JUSTIFIED,BLANK_FILLED)  +
            formatField(pp.getDescription(),12,LEFT_JUSTIFIED,BLANK_FILLED) +
            MakeSapolRMH.getDate() +
            formatField("",40,true,true));

//建立交易行

    BigDecimal totals = new BigDecimal(0);

    HashMap<String, WDETotalsByDescription> tempList = new HashMap<String, WDETotalsByDescription>();


//find duplicates

       Map<Pair, Pair> pairMap = new HashMap<Pair, Pair>();

        for (String line : lines) {
            String[] lineparts = line.split(",");

            if (line.startsWith("Date") || lineparts[3].equals("0.00") || lineparts[3].equals("-0.00")
                    || lineparts[3].equals("000") || lineparts[3].equals("0000") || lineparts[3].equals("00000")) {
                continue;
            }

            String description = lineparts[4];
            String acct = lineparts[2];
            String amt = lineparts[3];

            Pair newPair = new Pair(description, acct, amt);

            if (!pairMap.containsKey(newPair)) {
                pairMap.put(newPair, newPair);
            } else {
                Pair existingPair = pairMap.get(newPair);

                BigDecimal mergedAmount = new BigDecimal(existingPair.getAmount()).movePointRight(2).add((new BigDecimal(newPair.getAmount()).movePointRight(2)));
                existingPair.setAmount(mergedAmount.toString());
            }
        }

        Set<Pair> mergedPairs = pairMap.keySet();

////////////////////

    for (String linefromFile:lines){

        String[] lineparts = linefromFile.split(",");

        if ( linefromFile.startsWith("Date") || lineparts[3].equals("0.00") || lineparts[3].equals("-0.00") || lineparts[3].equals("000") || lineparts[3].equals("0000") || lineparts[3].equals("00000") ) {
            continue;
        }

        for(Pair p:mergedPairs) {

        WDETotalsByDescription wde = new WDETotalsByDescription();

        String line = new String("1");

        line += formatField (lineparts[1], 7, RIGHT_JUSTIFIED, BLANK_FILLED);
        line += formatField (lineparts[2], 9, RIGHT_JUSTIFIED, BLANK_FILLED);
        line += " " + formatField(pp.getTransactionCode(),2,LEFT_JUSTIFIED,ZERO_FILLED);

        wde.setStart(line);
        wde.setAmount(new BigDecimal(p.getAmount()));

        line = formatField (lineparts[4], 32, LEFT_JUSTIFIED, BLANK_FILLED);
        line += formatField (pp.getExernalDescription(), 18, LEFT_JUSTIFIED, BLANK_FILLED);
        line += formatField (lineparts[5], 7, RIGHT_JUSTIFIED, BLANK_FILLED);
        line += formatField (lineparts[6], 9, RIGHT_JUSTIFIED, BLANK_FILLED);
        line += formatField (pp.getNameOfRemitter(), 16, LEFT_JUSTIFIED, BLANK_FILLED);
        line += formatField ("", 8, RIGHT_JUSTIFIED, ZERO_FILLED);

        wde.setEnd(line);
        wde.setAccount(lineparts[4]);

        if(!tempList.containsKey(wde.getAccount())){
            tempList.put(wde.getAccount(), wde);
        }
        else{
            WDETotalsByDescription existingWDE = tempList.get(wde.getAccount());
            existingWDE.setAmount(existingWDE.getAmount().add(wde.getAmount()));
            tempList.put(existingWDE.getAccount(), existingWDE);
        }

        }
    }

    for(WDETotalsByDescription wde:tempList.values()){

        String line = new String();

        line = wde.getStart()
            + formatField(wde.getAmount().toString(), 10, RIGHT_JUSTIFIED, ZERO_FILLED)
            + wde.getEnd();

        if (formatField(wde.getAmount().toString(), 10, RIGHT_JUSTIFIED, ZERO_FILLED) != "0000000000") {
            totals = totals.add(wde.getAmount());
            fileLines.add(line);
        }
    }

//进行偏移记录，2012 年 11 月请求。

    String offset = new String();

    offset += "1";
    offset += pp.getAccountNumber(); // ###-### ######## (or else they will have to use spaces (###-###   ######)) 16 chars total
    offset += " ";

    if (pp.isCredit()){
        offset += "50";
    } else {
        offset += "13";
    }

    offset += formatField(totals.toString(), 10, RIGHT_JUSTIFIED, ZERO_FILLED);
    offset += formatField(pp.getNameOfRemitter(), 16, LEFT_JUSTIFIED, BLANK_FILLED);
    offset += "   " +
    formatField(pp.getInternalDescription(), 28, RIGHT_JUSTIFIED, BLANK_FILLED) +
    "   ";
    offset += pp.getAccountNumber(); // ###-### ######## (or else they will have to use spaces (###-###   ######)) 16 chars total
    offset += formatField(pp.getNameOfRemitter(), 16, LEFT_JUSTIFIED, BLANK_FILLED);
    offset += "00000000";

    fileLines.add(offset);

//制作预告片记录

    String trailerRecord = "7999-999            ";

    trailerRecord += formatField("", 10, RIGHT_JUSTIFIED, ZERO_FILLED);
    trailerRecord += formatField(totals.toString(), 10, RIGHT_JUSTIFIED, ZERO_FILLED);
    trailerRecord += formatField(totals.toString(), 10, RIGHT_JUSTIFIED, ZERO_FILLED);
    trailerRecord += formatField("", 24, RIGHT_JUSTIFIED, BLANK_FILLED);
    trailerRecord += formatField(Integer.toString(fileLines.size()-1), 6, RIGHT_JUSTIFIED, ZERO_FILLED);
    trailerRecord += formatField("", 40, RIGHT_JUSTIFIED, BLANK_FILLED);
    fileLines.add(trailerRecord);

    return fileLines;
}
}

Answer 1

您可以使用 HashMap<Pair, Pair>解决这个问题:

    Map<Pair, Pair> pairMap = new HashMap<Pair, Pair>();

    for (String line : lines) {
        String[] lineparts = line.split(",");

        if (line.startsWith("Date") || lineparts[3].equals("0.00") || lineparts[3].equals("-0.00")
                || lineparts[3].equals("000") || lineparts[3].equals("0000") || lineparts[3].equals("00000")) {
            continue;
        }

        String description = lineparts[4];
        String acct = lineparts[2];
        String amt = lineparts[3];

        Pair newPair = new Pair(description, acct, amt);
        if (!pairMap.containsKey(newPair)) {
            pairMap.put(newPair, newPair);
        } else {
            Pair existingPair = pairMap.get(newPair);
            String mergedAmount = existingPair.getAmount() + newPair.getAmount();
            existingPair.setAmount(mergedAmount);
        }
    }

    Set<Pair> mergedPairs = pairMap.keySet();

为此，Pair必须override hashCode and equals ，这样两个不同的Pair如果键和值相等，则认为实例相等。下面是一个由 Eclipse 生成的示例实现:

@Override
public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + ((key == null) ? 0 : key.hashCode());
    result = prime * result + ((value == null) ? 0 : value.hashCode());
    return result;
}

@Override
public boolean equals(Object obj) {
    if (this == obj) {
        return true;
    }
    if (obj == null) {
        return false;
    }
    if (getClass() != obj.getClass()) {
        return false;
    }
    Pair other = (Pair) obj;
    if (key == null) {
        if (other.key != null) {
            return false;
        }
    } else if (!key.equals(other.key)) {
        return false;
    }
    if (value == null) {
        if (other.value != null) {
            return false;
        }
    } else if (!value.equals(other.value)) {
        return false;
    }
    return true;
}