很多次我需要根据不同的字段对对象列表进行排序，最后我编写了一个比较器，它使用反射根据给定的一个或多个方法对列表进行排序。是否有一个框架已经实现了类似的功能？ Java 中是否已经实现了这个功能？ (我在SO中搜索了java比较器框架，并找到了35个似乎没有解决这个问题的命中)。
类似这样的事情:
基于给定方法比较事物的比较器:
package org.myframework.util.comparator;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class SimpleComparator implements Comparator<Object> {
//
// instance variables
//
private ArrayList<Method> methods;
//
// constructors
//
public SimpleComparator() {
this.methods = new ArrayList<Method>();
}
//
// trivial getters and setters
//
public ArrayList<Method> getMethods() {
return methods;
}
public void setMethods(ArrayList<Method> methods) {
this.methods = methods;
}
//
// implementation of compare
//
@Override
public int compare(Object o1, Object o2) {
for (Method method : this.methods) {
int diff = this.compare(o1, o2, method);
if (diff != 0) {
return diff;
}
}
return 0;
}
private int compare(Object o1, Object o2, Method method) {
try {
Object[] args = {};
Comparable value1 = (Comparable) method.invoke(o1, args);
Comparable value2 = (Comparable) method.invoke(o2, args);
if (value1 == null && value2 == null) {
return 0;
} else if (value1 == null) {
return 1;
} else if (value2 == null) {
return -1;
} else {
return value1.compareTo(value2);
}
} catch (Exception exp) {
throw new RuntimeException(exp);
}
}
public static <T> void sort(List<T> list, Class<T> cls, String methodName) {
try {
SimpleComparator comp = new SimpleComparator();
Class[] parameterTypes = {};
Method method = cls.getMethod(methodName, parameterTypes);
comp.getMethods().add(method);
Collections.sort(list, comp);
} catch (Exception exp) {
throw new RuntimeException(exp);
}
}
public static <T> void sort(List<T> list, Class<T> cls, String[] methodNames) {
try {
SimpleComparator comp = new SimpleComparator();
Class[] parameterTypes = {};
for(String methodName : methodNames) {
Method method = cls.getMethod(methodName, parameterTypes);
comp.getMethods().add(method);
}
Collections.sort(list, comp);
} catch (Exception exp) {
throw new RuntimeException(exp);
}
}
}
可排序事物的示例事物类:
package org.myframework.util.comparator;
public class Thing {
//
// instance variables
//
private String name;
private String color;
private String hue;
private int number;
private float cost;
//
// constructor
//
public Thing(String name, String color, String hue, int number, float cost) {
super();
this.name = name;
this.color = color;
this.hue = hue;
this.number = number;
this.cost = cost;
}
//
// trivial getters and setters
//
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
public String getHue() {
return hue;
}
public void setHue(String hue) {
this.hue = hue;
}
public int getNumber() {
return number;
}
public void setNumber(int number) {
this.number = number;
}
public float getCost() {
return cost;
}
public void setCost(float cost) {
this.cost = cost;
}
}
我希望能够做的事情的一个例子:
package org.myframework.util.comparator;
import java.util.ArrayList;
import java.util.List;
public class Example {
public static void main(String[] args) {
Thing thing1 = new Thing("thing1", "red ", null, 1, 1.00f);
Thing thing2 = new Thing("thing2", "green", null, 2, 100.00f);
Thing thing3 = new Thing("thing3", "orange", null, 3, 3.00f);
Thing thing4 = new Thing("thing4", "yellow", null, 4, 4.00f);
Thing thing5 = new Thing("thing5", "red ", "pink", 5, 5.00f);
Thing thing6 = new Thing("thing6", "red ", "maroon", 6, 6.00f);
Thing thing7 = new Thing("thing7", "red ", "candy", 7, 7.00f);
Thing thing8 = new Thing("thing8", "red ", "fire", 8, 8.00f);
ArrayList<Thing> things = new ArrayList<Thing>();
things.add(thing2);
things.add(thing4);
things.add(thing6);
things.add(thing8);
things.add(thing7);
things.add(thing5);
things.add(thing3);
things.add(thing1);
// the unsorted list
System.out.println("\n\nBefore sort:");
showList(things);
// sort by name
SimpleComparator.sort(things, Thing.class, "getName");
System.out.println("\n\nSorted by name:");
showList(things);
// sort by color
SimpleComparator.sort(things, Thing.class, "getColor");
System.out.println("\n\nSorted by color:");
showList(things);
// sort by hue
SimpleComparator.sort(things, Thing.class, "getHue");
System.out.println("\n\nSorted by hue:");
showList(things);
// sort by color and hue
String[] colorAndHue = { "getColor", "getHue" };
SimpleComparator.sort(things, Thing.class, colorAndHue);
System.out.println("\n\nSorted by color and hue:");
showList(things);
// sort by cost
SimpleComparator.sort(things, Thing.class, "getCost");
System.out.println("\n\nSorted by cost:");
showList(things);
}
private static void showList(List<Thing> things) {
for (Thing thing : things) {
System.out.println(thing.getName() + "\t" + thing.getColor() + "\t" + thing.getHue() + "\t" + thing.getNumber() + "\t" + thing.getCost());
}
}
}
此示例的输出:
Before sort:
thing2 green null 2 100.0
thing4 yellow null 4 4.0
thing6 red maroon 6 6.0
thing8 red fire 8 8.0
thing7 red candy 7 7.0
thing5 red pink 5 5.0
thing3 orange null 3 3.0
thing1 red null 1 1.0
Sorted by name:
thing1 red null 1 1.0
thing2 green null 2 100.0
thing3 orange null 3 3.0
thing4 yellow null 4 4.0
thing5 red pink 5 5.0
thing6 red maroon 6 6.0
thing7 red candy 7 7.0
thing8 red fire 8 8.0
Sorted by color:
thing2 green null 2 100.0
thing3 orange null 3 3.0
thing1 red null 1 1.0
thing5 red pink 5 5.0
thing6 red maroon 6 6.0
thing7 red candy 7 7.0
thing8 red fire 8 8.0
thing4 yellow null 4 4.0
Sorted by hue:
thing7 red candy 7 7.0
thing8 red fire 8 8.0
thing6 red maroon 6 6.0
thing5 red pink 5 5.0
thing2 green null 2 100.0
thing3 orange null 3 3.0
thing1 red null 1 1.0
thing4 yellow null 4 4.0
Sorted by color and hue:
thing2 green null 2 100.0
thing3 orange null 3 3.0
thing7 red candy 7 7.0
thing8 red fire 8 8.0
thing6 red maroon 6 6.0
thing5 red pink 5 5.0
thing1 red null 1 1.0
thing4 yellow null 4 4.0
Sorted by cost:
thing1 red null 1 1.0
thing3 orange null 3 3.0
thing4 yellow null 4 4.0
thing5 red pink 5 5.0
thing6 red maroon 6 6.0
thing7 red candy 7 7.0
thing8 red fire 8 8.0
thing2 green null 2 100.0
最佳答案
从您提供的示例来看，似乎使用 Comparator.comparing在 Java 8 中，传递方法引用将是一个解决方案。
编辑:在OP请求后添加简单示例
Collections.sort(Comparator.comparing(Thing::getHue));
关于java - 是否有一个 Java 框架可以实现一个简单灵活的多用途比较器，可以与 Java 1.7 一起使用，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/32502084/