如何使用Java创建csv文件中具有相同行名的所有值的列表?

Question

我使用的Excel文件

我想解析一个csv文件并提取名称，如"椅子"，然后是每种可能颜色的列表，所以['蓝色'，'绿色'，'黄色']。我该怎么做呢?

我已经创建了一个类Object，它有一个'String name'和一个' listcolors '。

CSVReader reader = new CSVReader(new FileReader(new File(url.toURI()).getAbsolutePath()));
Object<API> listings = new ArrayList<Object>();
String [] line;
List<String> colourList = new ArrayList<>();
reader.readNext();
while ((line = reader.readNext()) != null) {
String name = line[0];
String colour = line[1];
colourList.add(operation);
Object object = new Object(name,colourList);
listings.add(object);
}

Answer 1

您可以创建一个Hashmap，其中key为项目名称，value为可用颜色列表。

我希望下面的片段将解决您的问题。祝你好运! !

HashMap<String,List<String>> data = new HashMap<>();
String [] line;
reader.readNext();
while ((line = reader.readNext()) != null) {
String name = line[0];
String colour = line[1];
if(data.containsKey(name.toLowerCase())){
data.get(name.toLowerCase()).add(colour.toLowerCase());
}
else{
List<String> colorList = new ArrayList<>();
colorList.add(colour.toLowerCase());
data.put(name.toLowerCase(),colorList);
}
}

Answer 2

@g00se你说的'流分组操作'是什么意思

我给你看。实际上，在您的示例中，由于使用的是适当的csv API，因此可以利用它先创建bean，然后再进行分组。这就是我所说的流分组的意思:我们创建一个Map<String, HouseholdObject>>(是的，这是我为你的实体取的名字——可惜它里面有"对象"这个词，但没关系)。将它们收集到具有相同名称的组中:

package com.technojeeves.opencsvbeans;
import com.opencsv.bean.CsvToBeanBuilder;
import java.util.List;
import java.util.Map;
import static java.util.stream.Collectors.*;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
public class HouseholdParser {
public static void main(String[] args) {
try {
List<HouseholdObject> objects = new HouseholdParser().read(new File(args[0]));
Map<String, List<HouseholdObject>> objectsGroupedByName = 
objects.stream()
.skip(1)
.collect(groupingBy(HouseholdObject::getName));
System.out.println("The following groups of household objects were found:");
objectsGroupedByName.entrySet()
.stream()
.forEach(e -> {
System.out.println(e.getKey());
e.getValue()
.stream()
.forEach(v -> System.out.printf("t%s%n", v.getColour()));
});

} catch (Throwable t) {
t.printStackTrace();
}
}
public List<HouseholdObject> read(File file) {
try (FileReader reader = new FileReader(file)) {
return new CsvToBeanBuilder(reader).withType(HouseholdObject.class).build().parse();
} catch (IOException e) {
throw new RuntimeException("Cannot read file: " + file.getName() + e);
}
}
}

这是我为它做的豆:

package com.technojeeves.opencsvbeans;
import com.opencsv.bean.CsvBindByPosition;
import com.opencsv.bean.CsvCustomBindByPosition;
import com.opencsv.bean.AbstractBeanField;
import com.opencsv.bean.CsvRecurse;
public class HouseholdObject {
@CsvBindByPosition(position = 0)
private String name;
@CsvBindByPosition(position = 1)
private String colour;
public HouseholdObject() {
}
public HouseholdObject(String name, String colour) {
this.name = name;
this.colour = colour;
}
public String getName() {
return this.name;
}
public String getColour() {
return this.colour;
}
public void setName(String name) {
this.name = name;
}
public void setColour(String colour) {
this.colour = colour;
}
@Override
public String toString() {
return String.format("%s=%s,%s=%s", "name", name, "colour", colour);
}
@Override
public boolean equals(Object o) {
HouseholdObject other = (HouseholdObject)o;
return name.equals(other.name) && colour.equals(other.colour);
}
@Override
public int hashCode() {
return name.hashCode() * colour.hashCode();
}
}

这是我的输出与你的源CSV:

The following groups of household objects were found:
Table
Purple
Pink
Chair
Blue
Green
Yellow
Door
Yellow