使用Comparator對象作為參數
需要注意的是：排序方法是針對鍵的，而不是值的。如果想針對值，需要更麻煩的一些方法（重寫一些方法）
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TreeMap<Screen,Integer> res = new TreeMap<Screen, Integer>(new Comparator<Screen>() { @Override public int compare(Screen screen1, Screen t1) { // 定義TreeMap的排序方法 return screen1.compareTo(t1); // TreeMap的排序方法是：調用screen的比較方法 } }); |
2. 定義里面的對象的比較方法
繼承Comparable接口
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public class Screen implements Comparable{ private double size,price; ... @Override public int compareTo(Object s){ // 定義比較方法 Screen screen = (Screen)s; return this.price>screen.getPrice()?-1:1; // 返回負整數和正整數 }} |
3. 所有代碼
按照Screen的價錢排序
Screen.java
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import java.util.*;import java.lang.Integer;public class Screen implements Comparable{ private double size,price; public Screen(){} public void setSize(double size){ this.size = size; } public void setPrice(double price){ this.price = price; } public double getSize(){ return this.size;} public double getPrice() { return this.price;} public void show(){ System.out.println("size is: "+this.size+"; price is: "+this.price); } @Override public int compareTo(Object s){ // 定義比較方法 Screen screen = (Screen)s; return this.price>screen.getPrice()?-1:1; // 返回負整數和正整數 }} |
TestScreen.java
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import java.util.Comparator;import java.util.Scanner;import java.util.TreeMap;import problem2.Screen;public class TestScreen { final static int MAX_NUM = 8; public static void main(String []args){ TreeMap<Screen,Integer> res = new TreeMap<Screen, Integer>(new Comparator<Screen>() { @Override public int compare(Screen screen1, Screen t1) { // 定義TreeMap的排序方法 return screen1.compareTo(t1); // TreeMap的排序方法是：調用screen的比較方法 } }); double price, size; Scanner scan = new Scanner(System.in); for(int i=0;i<MAX_NUM;++i){ Screen screen = new Screen(); size = scan.nextDouble(); price = scan.nextDouble(); screen.setSize(size); screen.setPrice(price); res.put(screen,i); } for(Screen screen:res.keySet()){ screen.show(); } return ; }}// 測試樣例（輸入）// 1 2// 3 4// 5 6// 7 8// 9 10// 1 2// 3 4// 3 4 |
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原文鏈接：http://www.jianshu.com/p/dc0e6c3a7c67
