《Java语言程序设计与数据结构》编程练习答案（第二十章）（二）

英文名：Introduction to Java Programming and Data Structures, Comprehensive Version, 11th Edition

20.9

public class book {
       public static void main(String[] args) {
           Scanner input = new Scanner(System.in);        Comparator
   
     circleComparator = new Comparator
    
     () {
               @Override            public int compare(Circle o1, Circle o2) {
                   return (int)(o2.getRadius()-o1.getRadius());            }        };        PriorityQueue
     
       test = new PriorityQueue<>(1, circleComparator);        for(int i=0;i<10;i++){
               test.add(new Circle(20*Math.random()));        }        for(int i=0;i<10;i++){
               System.out.println(test.remove().getRadius());        }    }}class Circle{
       private double radius;    private double square;    public Circle(double r){
           this.radius = r;        this.square = Math.PI*r*r;    }    public double getRadius(){
           return this.radius;    }    public double getSquare(){
           return this.square;    }}

20.10

public class book {
       public static void main(String[] args) {
           Scanner input = new Scanner(System.in);        PriorityQueue
   
     set1 = new PriorityQueue<>();        PriorityQueue
    
      set2 = new PriorityQueue<>();        set1.offer("George");        set1.offer("Jim");        set1.offer("John");        set1.offer("Blake");        set1.offer("Kevin");        set1.offer("Michael");        set2.offer("George");        set2.offer("Katie");        set2.offer("Kevin");        set2.offer("Michelle");        set2.offer("Ryan");        PriorityQueue
     
       union = new PriorityQueue<>(set1);        for( String str: set2){
               if(!union.contains(str)){
                   union.offer(str);            }        }        PriorityQueue
      
        intersect = new PriorityQueue<>();        for(String str : set1){
               if(set2.contains(str)){
                   intersect.offer(str);            }        }        PriorityQueue
       
         diff = new PriorityQueue<>();        for(String str: set1){
               if(!set2.contains(str)){
                   diff.offer(str);            }        }        System.out.println(Arrays.toString(union.toArray()));        System.out.println(Arrays.toString(intersect.toArray()));        System.out.println(Arrays.toString(diff.toArray()));    }}

20.11

public class book {
       public static void main(String[] args) {
           Scanner input = new Scanner(System.in);        System.out.println("Please enter the code: ");        String code = input.nextLine();        boolean isPair = true;        Stack
   
     test = new Stack<>();        for(int i=0;i

20.12

public class book {
       public static void main(String[] args) {
           Scanner input = new Scanner(System.in);                MyPriorityQueue
   
     test = new MyPriorityQueue<>();        test.offer("114");        test.offer("514");        MyPriorityQueue
    
      test1 = (MyPriorityQueue
     
      ) test.clone();        test1.offer("1919810");        System.out.println(Arrays.toString(test.toArray()));        System.out.println(Arrays.toString(test1.toArray()));    }}class MyPriorityQueue
      
        extends PriorityQueue
       
         implements Cloneable{
       @Override    protected Object clone(){
           MyPriorityQueue
        
          myPriorityQueue = null; try{ myPriorityQueue = (MyPriorityQueue
         
          ) super.clone(); }catch (CloneNotSupportedException e){ e.printStackTrace(); } return myPriorityQueue; }}

20.13

🐎

20.14

public class book {
       public static void main(String[] args) {
           Scanner input = new Scanner(System.in);        Stack
   
     test = new Stack<>();        System.out.println("Please enter the RPN");        String rpn = input.nextLine();        rpn = rpn.replace(" ","");        for(int i=0;i
    
     = '0' && tmp <='9'){
                   test.push((char)(tmp-'0'));            }            else{
                   int op1 = (int)test.pop();                int op2 = (int)test.pop();                int res;                switch (tmp){
                       case '+':                        res = op1 + op2;                        test.push((char)res);                        break;                    case '-':                        res = op1 - op2;                        test.push((char)res);                        break;                    case '*':                        res = op1 * op2;                        test.push((char)res);                        break;                    case '/':                        res = op1 / op2;                        test.push((char)res);                        break;                    default:                        break;                }            }        }        System.out.println("The result is "+(int)(test.pop()));    }}

20.15

🐔

20.16

参见

20.17

👨🐰🌶

20.18

20.21

public class book {
       public static void main(String[] args) {
           Scanner input = new Scanner(System.in);        String[] list2 = {
   "red","blue","green","yellow","orange","pink"};        Comparator
   
     comparator = new Comparator
    
     () {
               @Override            public int compare(String o1, String o2) {
                   return o1.charAt(o1.length()-1)-o2.charAt(o2.length()-1);            }        };        selectionSort(list2, comparator);        System.out.println(Arrays.toString(list2));    }    public static 
     
       void selectionSort(T[] list, Comparator< ? super T> comparator){
           for(int i=0;i