基于列的排序行

Question

有什么方法可以根据列进行排序？

我有一个像，线条

1000 Australia  Kangaroo   Canberra 
1002 India   Tiger    Delhi 
1092 Germany  Eagle    Berlin 

以上线具有基于第二列进行排序，即澳大利亚，德国，印度。

所以，结果应该是，

1000 Australia  Kangaroo   Canberra 
1092 Germany  Eagle    Berlin 
1002 India   Tiger    Delhi 

数据是从文本文件

Answer 1

我建议你阅读行文件中的行和使用的StringTokenizer每行有机会获得单话。然后你可以把每一行放到一个以国家为关键字的HashMap中。

使用

Collection<String> k = yourHashMap.keySet(); 
Collections.sort(k); 

能够时不时的关键自然顺序设置。然后，您可以遍历密钥集并以排序的方式访问hashmap中的每一行。

Answer 2

我建议您使用TreeSet并阅读您的文本文件并将您的数据保存在实现Comparable的类中。这样，当您添加到TreeSet时，数据将按排序顺序添加。

这个例子可能会有帮助：

class Data implements Comparable<Data>{ 

    private int digits; 
    private String country; 
    private String animal; 
    private String capital; 

    public Data(int digits, String country, String animal, String capital){ 
     this.digits = digits; 
     this.country = country; 
     this.animal = animal; 
     this.capital = capital; 
    } 

    public int getDigits() { 
     return digits; 
    } 

    public void setDigits(int digits) { 
     this.digits = digits; 
    } 

    public String getCountry() { 
     return country; 
    } 

    public void setCountry(String country) { 
     this.country = country; 
    } 

    public String getAnimal() { 
     return animal; 
    } 

    public void setAnimal(String animal) { 
     this.animal = animal; 
    } 

    public String getCapital() { 
     return capital; 
    } 

    public void setCapital(String capital) { 
     this.capital = capital; 
    } 

    @Override 
    public int compareTo(Data data) { 
     return getCountry().compareTo(data.getCountry()); 
    } 
} 


class TestCountry{ 
    public static void main(String[] args) { 
     TreeSet<Data> set = new TreeSet<Data>(); 
     /** 
     * Assuming that you can read the CSV file and build up the Data objects. 
     * You would then put them in the set where they will be added in a sorted 
     * fashion 
     */ 
     set.add(new Data(1000, "Australia", "Kangaroo", "Canberra")); 
     set.add(new Data(1002, "India", "Tiger", "Delhi")); 
     set.add(new Data(1092, "Germany", "Eagle", "Berlin")); 

     for(Data data: set){ 
      System.out.println(data.getDigits()+"\t"+data.getCountry()+"\t"+data.getAnimal()+"\t"+data.getCapital()); 
     } 
    } 
} 

Answer 3

可以结构数据，因为这模型

行类代表行数据

public class Row implements Comparable<Row> { 

private int number; 
private String country; 
private String animal; 
private String city; 

public Row(int number, String country, String animal, String city) { 
    super(); 
    this.number = number; 
    this.country = country; 
    this.animal = animal; 
    this.city = city; 
} 

public int getNumber() { 
    return number; 
} 

public void setNumber(int number) { 
    this.number = number; 
} 

public String getCountry() { 
    return country; 
} 

public void setCountry(String country) { 
    this.country = country; 
} 

public String getAnimal() { 
    return animal; 
} 

public void setAnimal(String animal) { 
    this.animal = animal; 
} 

public String getCity() { 
    return city; 
} 

public void setCity(String city) { 
    this.city = city; 
} 

// Easy to print and show the row data 
@Override 
public String toString() { 
    return "Row [number=" + number + ", country=" + country + ", animal=" 
      + animal + ", city=" + city + "]"; 
} 

// sort based on column "country" 
@Override 
public int compareTo(Row o) { 
    return this.country.compareTo(o.country); 
} 

}

和测试示例将作为

public static void main(String[] args) { 

    ArrayList<Row> data = new ArrayList<Row>(); 
    data.add(new Row(1000, "Australia", "Kangaroo", "Canberra")); 
    data.add(new Row(1002, "India", "Tiger", "Delhi")); 
    data.add(new Row(1092, "Germany", "Eagle", "Berlin")); 

    // To sort the data (based on column "country") 
    Collections.sort(data); 

    // Print and show the data 
    for (int i = 0; i < data.size(); i++) { 
     System.out.println(data.get(i)); 
    } 


}