java 中 Integer 跟 double类型相乘还有比较的问题

今早遇到了一个问题?Integer 跟 double类型相乘的问题

eg1:

Integer packSize = 2;Integer qty = 7;Double nw = 20.4;int result = qty - qty % packSize;System.out.println(qty % packSize);System.out.println(qty - qty % packSize);System.out.println(nw * result);

?输出结果：

6122.39999999999999

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eg2:

Integer packSize = 2;Integer qty = 7;Double nw = <font color="#FF0000">20.5</font>;int result = qty - qty % packSize;System.out.println(qty % packSize);System.out.println(qty - qty % packSize);System.out.println((float)nw * result);

输出结果：

6122.4

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然后我选者了BigDecimal

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eg：

public static void main(String arg[]){   BigDecimal bd = new BigDecimal("0");   bd = bd.add(new BigDecimal("99.99"));   bd = bd.add(new BigDecimal("1.99"));   System.out.println("BigDecimal result " + bd);   double d = 99.99;   d = d + 1.99;   System.out.println("Double result " + d);}

输出结果为：

BigDecimal result 101.98Double result 101.97999999999999

然后我这样做的：

Double    grossWeight;//.....@Transient??? public Integer getRemainder() {??? ??? return qty % packSize;??? }?@Transient    public Double getGrossWeights() {        return grossWeight * getRemainder();    }

因为我上一级要做加法运算

@Transientpublic Double getTotalGrossWeightAmount() {class EntrySubTotalVisitor implements Visitor<ShipmentRecordEntry> {Double totalGrossWeightAmount = 0.0;public void visit(final ShipmentRecordEntry entry) {totalGrossWeightAmount += entry.getGrossWeights();}}EntrySubTotalVisitor visitor = new EntrySubTotalVisitor();Algorithms.traverse(shipmentRecordEntries, visitor);return visitor.totalGrossWeightAmount;}

?so：

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我的测试是这样写的

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import org.testng.annotations.Test;import java.math.BigDecimal;@Testpublic void testGetGrossWeights() {ShipmentRecordEntry entry = new ShipmentRecordEntry();entry.setQty(7);entry.setPackSize(2);entry.setGrossWeight(20.4);BigDecimal bd = new BigDecimal(entry.getGrossWeights());assert String.valueOf(bd.floatValue()).equals("122.4") : String.valueOf(bd.floatValue());}

测试pass。

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