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Jakarta Commons Lang ComparaToBuilder.class
このクラスを使うと簡単に、(compara)比較を実装することができます。
使い方はコードを見ていただければと思います。
例
Bookクラスを使った例
Bookクラスがあります。これはtitle・author・price ３つのプロパティーを持っています。
いきなり話が飛躍しますが、
このBookクラスをソートする属性をしていできるBookComparatorを作りました。
これを使うことで、Bookをtitle・author・priceのいずれでソートするか。昇順にするか降順にするかしていできます。
出力結果
{about Java,jack,2000,at java,lord,100,everything Java,tom,500,my java,bob,3000}
{my java,bob,3000,everything Java,tom,500,at java,lord,100,about Java,jack,2000}
{my java,bob,3000,about Java,jack,2000,at java,lord,100,everything Java,tom,500}
{everything Java,tom,500,at java,lord,100,about Java,jack,2000,my java,bob,3000}
{at java,lord,100,everything Java,tom,500,about Java,jack,2000,my java,bob,3000}
{my java,bob,3000,about Java,jack,2000,everything Java,tom,500,at java,lord,100}
プログラム
List list=new Vector();
list.add(new Book("about Java","jack",2000));
list.add(new Book("everything Java","tom",500));
list.add(new Book("my java","bob",3000));
list.add(new Book("at java","lord",100));
Book[] books=(Book[])list.toArray(new Book[list.size()]);
BookComparator bc=new BookComparator();
bc.setType(BookComparator.TITLE);
bc.setAscending(true);
Arrays.sort(books,bc);
System.out.println(ArrayUtils.toString(books));
bc.setType(BookComparator.TITLE);
bc.setAscending(false);
Arrays.sort(books,bc);
System.out.println(ArrayUtils.toString(books));
bc.setType(BookComparator.AUTHOR);
bc.setAscending(true);
Arrays.sort(books,bc);
System.out.println(ArrayUtils.toString(books));
bc.setType(BookComparator.AUTHOR);
bc.setAscending(false);
Arrays.sort(books,bc);
System.out.println(ArrayUtils.toString(books));
bc.setType(BookComparator.PRICE);
bc.setAscending(true);
Arrays.sort(books,bc);
System.out.println(ArrayUtils.toString(books));
bc.setType(BookComparator.PRICE);
bc.setAscending(false);
Arrays.sort(books,bc);
System.out.println(ArrayUtils.toString(books));
■Book.java
package test;
/**
*
*
*/
public class Book {
private int price;
private String title;
private String author;
public Book(String title,String author,int price){
this.title=title;
this.author=author;
this.price=price;
}
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
this.author = author;
}
public int getPrice() {
return price;
}
public void setPrice(int price) {
this.price = price;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String toString(){
return title+","+author+","+price;
}
}
■BookComparator.java
/*
* Created on 2004/10/22
* Author aki@www.xucker.jpn.org
* License Apache2.0 or Common Public License
*/
package test;
import java.util.Comparator;
import org.apache.commons.lang.builder.CompareToBuilder;
/**
*
*
*/
public class BookComparator implements Comparator{
private int type;
public boolean isAscending() {
return ascending;
}
public void setAscending(boolean ascending) {
this.ascending = ascending;
}
public int getType() {
return type;
}
public void setType(int type) {
this.type = type;
}
public final static int TITLE=0;
public final static int AUTHOR=1;
public final static int PRICE=2;
/* (non-Javadoc)
* @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
*/
public int compare(Object o1, Object o2) {
if(o1 instanceof Book && o2 instanceof Book){
Book book1;
Book book2;
if(ascending){
book1=(Book)o1;
book2=(Book)o2;
}else{
book1=(Book)o2;
book2=(Book)o1;
}
CompareToBuilder builder= new CompareToBuilder();
if(type==TITLE){
builder.append(book1.getTitle(),book2.getTitle()).append(book1.getAuthor(),book2.getAuthor()).append(book1.getPrice(),book2.getPrice());
}
else if(type==AUTHOR){
builder.append(book1.getAuthor(),book2.getAuthor()).append(book1.getTitle(),book2.getTitle()).append(book1.getPrice(),book2.getPrice());
}else if(type==PRICE){
builder.append(book1.getPrice(),book2.getPrice()).append(book1.getTitle(),book2.getTitle()).append(book1.getAuthor(),book2.getAuthor());
}
return builder.toComparison();
}else
return 0;
}
private boolean ascending=true;
}
汎用Bean用 Comparator
ソートをbean名で指定でき汎用的なComparatorを作ってみました。
BeanUtilsのPropertyUtilsを使っています。
実行速度は遅いと思いますが、手を抜きたいときには使えると思います。
/*
* Created on 2004/10/22
* Author aki@www.xucker.jpn.org
* License Apache2.0 or Common Public License
*/
package test;
import java.lang.reflect.InvocationTargetException;
import java.util.Comparator;
import org.apache.commons.beanutils.PropertyUtils;
import org.apache.commons.lang.builder.CompareToBuilder;
/**
*
*
*/
public class BeanComparator implements Comparator{
private String bean;
private boolean ascending=true;
public boolean isAscending() {
return ascending;
}
public void setAscending(boolean ascending) {
this.ascending = ascending;
}
public String getBean() {
return bean;
}
public void setBean(String bean) {
this.bean = bean;
}
public int compare(Object o1, Object o2) {
CompareToBuilder builder= new CompareToBuilder();
try {
if(ascending)
builder.append(PropertyUtils.getProperty(o1,bean),PropertyUtils.getProperty(o2,bean));
else
builder.append(PropertyUtils.getProperty(o2,bean),PropertyUtils.getProperty(o1,bean));
return builder.toComparison();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchMethodException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return 0;
}
}
