java 中 Integer 跟 double类型相乘还有比较的有关问题

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：

6
122.39999999999999

 

 

eg2:

Integer packSize = 2;
		Integer qty = 7;
		Double nw = <font class="Apple-style-span" 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：

6
122.4

 

然后我选者了BigDecimal

 

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 101.98

Double 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

@Transient
	public 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：

 

我的测试是这样写的

 

import org.testng.annotations.Test;
import java.math.BigDecimal;
@Test
	public 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。