Question

我希望将两个相同域对象的ArrayList组合并求和（特定属性）。根据多个属性匹配的条件，将它们合并为一个。

这是我的模型类

public class SalesTransactionTax {

  private String code;
  private BigDecimal rate;
  private Boolean isFixed;
  private BigDecimal taxAmount;

  public SalesTransactionTax(String code, BigDecimal rate, Boolean isFixed, BigDecimal taxAmount) { // NO_UCD
                                                                                                    // (unused
    // code)

    this.code = code;
    this.rate = rate;
    this.isFixed = isFixed;
    this.taxAmount = taxAmount;
  }

  public SalesTransactionTax() {

  }

  public String getCode() {

    return code;
  }

  public void setCode(String code) {

    this.code = code;
  }

  public BigDecimal getRate() {

    return rate;
  }

  public void setRate(BigDecimal rate) {

    this.rate = rate;
  }

  public Boolean getIsFixed() {

    return isFixed;
  }

  public void setFixed(Boolean fixed) {

    isFixed = fixed;
  }

  public BigDecimal getTaxAmount() {
    return taxAmount;
  }

  public void setTaxAmount(BigDecimal taxAmount) {
    this.taxAmount = taxAmount;
  }

  @Override
  public String toString() {
    return "SalesTransactionTax [code=" + code + ", rate=" + rate + ", isFixed=" + isFixed
        + ", taxAmount=" + taxAmount + "]";
  }

}

以下面的例子为例：

List<SalesTransactionTax> taxes  = new ArrayList<>();

taxes.add(new SalesTransactionTax("VAT_1", 5.000, true, 1.100));
taxes.add(new SalesTransactionTax("VAT_1", 5.000, true, 1.100));
taxes.add(new SalesTransactionTax("VAT_2", 9.000, true, 2.200));
taxes.add(new SalesTransactionTax("VAT_2", 9.000, true, 2.200));
taxes.add(new SalesTransactionTax("VAT_2", 9.000, true, 2.200));
taxes.add(new SalesTransactionTax("VAT_2", 9.000, false, 9.500));
taxes.add(new SalesTransactionTax("VAT_3", 7.000, true, 1.000));

新ArrayList中的值为：

VAT_1,5000，true，2.200
VAT_2,9.000，true，6.600
VAT_2,9.000，false，9.500
VAT_3,7.000，true，1.000

使用Java 8，可能会有一个Lambda表达式吗？感谢您的任何建议。

Answer 1

add (...)方法应该具有对税额进行求和的逻辑，为此，有必要检查新交易是否符合既定的验证。

验证应该相同：getCode(), getRate(), getIsFixed()

要添加的代码段

public void add(SalesTransactionTax inputValue) {
    SalesTransactionTax salesTransactionTax = checkInList(inputValue);
    if (salesTransactionTax != null) {
        // To sum operations the method used is add() from BigDecimal
        salesTransactionTax.setTaxAmount(salesTransactionTax.getTaxAmount().add(inputValue.getTaxAmount()));
    } else {
        this.salesTransactionTaxList.add(inputValue);
    }
}

要检查列表中是否存在新的SalesTransactionTax，您可以使用Java 8中的filter()方法进行验证

检查验证的代码段：

private SalesTransactionTax checkInList(SalesTransactionTax stt) {
    return salesTransactionTaxList.stream()
            // To compare String is used equals()
            .filter(stt2 -> stt2.getCode().equals(stt.getCode()))
            // To compare BigDecimal is used compareTo()
            .filter(stt2 -> stt2.getRate().compareTo(stt.getRate()) == 0)
            // To compare boolean is used ==
            .filter(stt2 -> stt2.getIsFixed() == stt.getIsFixed())
            // If doesn't exist return null
            .findAny().orElse(null);
}

完整示例：

import java.math.BigDecimal;
import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.List;

public class SalesTransactionTax {

    private String code;
    private BigDecimal rate;
    private Boolean isFixed;
    private BigDecimal taxAmount;
    private List<SalesTransactionTax> salesTransactionTaxList = null;

    public SalesTransactionTax(String code, BigDecimal rate, Boolean isFixed, BigDecimal taxAmount) { // NO_UCD
        this.code = code;
        this.rate = rate;
        this.isFixed = isFixed;
        this.taxAmount = taxAmount;
    }

    public SalesTransactionTax() {
        this.salesTransactionTaxList = new ArrayList<>();
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public BigDecimal getRate() {
        return rate;
    }

    public void setRate(BigDecimal rate) {
        this.rate = rate;
    }

    public Boolean getIsFixed() {
        return isFixed;
    }

    public void setFixed(Boolean fixed) {
        isFixed = fixed;
    }

    public BigDecimal getTaxAmount() {
        return taxAmount;
    }

    public void setTaxAmount(BigDecimal taxAmount) {
        this.taxAmount = taxAmount;
    }

    public void add(SalesTransactionTax inputValue) {
        SalesTransactionTax salesTransactionTax = checkInList(inputValue);
        if (salesTransactionTax != null) {
            // To sum operations the method used is add() from BigDecimal
            salesTransactionTax.setTaxAmount(salesTransactionTax.getTaxAmount().add(inputValue.getTaxAmount()));
        } else {
            this.salesTransactionTaxList.add(inputValue);
        }
    }

private SalesTransactionTax checkInList(SalesTransactionTax stt) {
    return salesTransactionTaxList.stream()
            // To compare String is used equals()
            .filter(stt2 -> stt2.getCode().equals(stt.getCode()))
            // To compare BigDecimal is used compareTo()
            .filter(stt2 -> stt2.getRate().compareTo(stt.getRate()) == 0)
            // To compare boolean is used ==
            .filter(stt2 -> stt2.getIsFixed() == stt.getIsFixed())
            // If doesn't exist return null
            .findAny().orElse(null);
}

    public void print() {
        salesTransactionTaxList.forEach(System.out::println);
    }

    @Override
    public String toString() {
        //Output formatted
        DecimalFormat df = new DecimalFormat("#,###.000");
        return code + ", " + df.format(new BigDecimal(String.valueOf(rate))) + ", " + isFixed + ", " + df.format(new BigDecimal(String.valueOf(taxAmount)));
    }

    public static void main(String[] args) {

        SalesTransactionTax mergeTaxes = new SalesTransactionTax();
        mergeTaxes.add(new SalesTransactionTax("VAT_1", BigDecimal.valueOf(5.000), true, BigDecimal.valueOf(1.100)));
        mergeTaxes.add(new SalesTransactionTax("VAT_1", BigDecimal.valueOf(5.000), true, BigDecimal.valueOf(1.100)));
        mergeTaxes.add(new SalesTransactionTax("VAT_2", BigDecimal.valueOf(9.000), true, BigDecimal.valueOf(2.200)));
        mergeTaxes.add(new SalesTransactionTax("VAT_2", BigDecimal.valueOf(9.000), true, BigDecimal.valueOf(2.200)));
        mergeTaxes.add(new SalesTransactionTax("VAT_2", BigDecimal.valueOf(9.000), true, BigDecimal.valueOf(2.200)));
        mergeTaxes.add(new SalesTransactionTax("VAT_2", BigDecimal.valueOf(9.000), false, BigDecimal.valueOf(9.500)));
        mergeTaxes.add(new SalesTransactionTax("VAT_3", BigDecimal.valueOf(7.000), true, BigDecimal.valueOf(1.000)));
        mergeTaxes.print();
    }

}

<强>输出：

VAT_1, 5.000, true, 2.200
VAT_2, 9.000, true, 6.600
VAT_2, 9.000, false, 9.500
VAT_3, 7.000, true, 1.000

Answer 2

你说

根据条件，如果两个属性匹配，则将它们组合在一起之一。

但根据示例结果，您需要检查三个属性匹配。

public class SalesTransactionMerge {

private List<SalesTransactionTax> taxes = null;

public List<SalesTransactionTax> getTaxes(){
    return this.taxes;
}

public SalesTransactionMerge(){
    this.taxes = new ArrayList<SalesTransactionTax>();
}

public void add(SalesTransactionTax stt){
    SalesTransactionTax sttExists = exists(stt);
    if(sttExists == null){
        this.taxes.add(stt);
    }
    else{
        sttExists.setTaxAmount(sttExists.getTaxAmount().add(stt.getTaxAmount()));
    }
}

private SalesTransactionTax exists(SalesTransactionTax stt){
    SalesTransactionTax sttExists = null;
    for(SalesTransactionTax stt2 : taxes){
        int matches = 0;
        if(stt2.getCode().equals(stt.getCode())) matches++;
        if(stt2.getRate().compareTo(stt.getRate()) == 0) matches++;
        if(stt2.getIsFixed() == stt.getIsFixed()) matches++;
        if(matches == 3){       
            sttExists = stt2;
            break;
        }
    }
    return sttExists;
}

public void print(){
    for(SalesTransactionTax stt : taxes){
        System.out.println(stt.toString());
    }
}
}

使用您的示例

public static void main(String[] args) {

    SalesTransactionMerge mergeTaxes = new SalesTransactionMerge();
    mergeTaxes.add(new SalesTransactionTax("VAT_1", BigDecimal.valueOf(5.000), true, BigDecimal.valueOf(1.100)));
    mergeTaxes.add(new SalesTransactionTax("VAT_1", BigDecimal.valueOf(5.000), true, BigDecimal.valueOf(1.100)));
    mergeTaxes.add(new SalesTransactionTax("VAT_2", BigDecimal.valueOf(9.000), true, BigDecimal.valueOf(2.200)));
    mergeTaxes.add(new SalesTransactionTax("VAT_2", BigDecimal.valueOf(9.000), true, BigDecimal.valueOf(2.200)));
    mergeTaxes.add(new SalesTransactionTax("VAT_2", BigDecimal.valueOf(9.000), true, BigDecimal.valueOf(2.200)));
    mergeTaxes.add(new SalesTransactionTax("VAT_2", BigDecimal.valueOf(9.000), false, BigDecimal.valueOf(9.500)));
    mergeTaxes.add(new SalesTransactionTax("VAT_3", BigDecimal.valueOf(7.000), true, BigDecimal.valueOf(1.000)));
    mergeTaxes.print();
}

将对象的ArrayList与Java中的BigDecimal相结合

2 个答案: