Java语言程序设计（第3版）沈泽刚主编第101112章课后习题答案

Java语⾔程序设计（第3版）沈泽刚主编第10，11，12章课后习题答案Java语⾔程序设计(第3版)沈泽刚主编第10，11，12章课后习题答案第10章接⼝和Lambda表达式定义Duck类实现Swimmable接⼝和flyable接⼝。interfaceinterfaceSwimmable{publicvoidswim();}interfaceflyable{publicvoidfly();}publicclassDuckimplementsSwimmable,flyable{@Overridepublicvoidswim(){System.out.println("Icanswimming");}@Overridepublicvoidfly(){System.out.println("Icanfly");}publicstaticvoidmain(String[]args){Duckduck=newDuck();duck.fly();duck.swim();Swimmablesduck//向上转换，⾃动类型转换s.swim();Duckd=(Duck)s;//向下转换，强制类型转换d.fly();d.swim();}}定义⼀个名为RandomIntSequence的类实现IntSequence接⼝。interfaceinterfaceIntSequence{publicbooleanhasNext();publicintnext();}publicclassRandomIntSequenceimplementsIntSequence{privateintn;@OverridepublicbooleanhasNext(){n=(int)(Math.random()*90+10);returntrue;}@Overridepublicintnext(){returnn;}publicstaticvoidmain(String[]args){RandomIntSequencer=newRandomIntSequence();if(r.hasNext()){System.out.println(r.next());}}}设计⼀个名为SequenceTest的类，在其中编写⼀个static⽅法⽤于计算⼀个整数n的平均值publicclasspublicclassSequenceTest{publicstaticdoubleaverage(IntSequenceseq,intn){doublesum=0.0;intm=n;while(seq.hasNext()&&m>0){sum+=seq.next();m--;}returnsum/n;}publicstaticvoidmain(String[]args){RandomIntSequencer=newRandomIntSequence();doubleave=average(r,10);System.out.println(ave);}}修改Employee的定义，让根据员⼯年龄进⾏⽐较publicclasspublicclassEmployeeimplementsComparable<Employee>{intid;intage;doublesalary;Stringname;publicEmployee(intid,Stringname,intage,doublesalary){this.id=id;this.age=age;this.salary==name;}@OverridepublicintcompareTo(Employeeemployee){returnemployee.age-this.age;}publicStringtoString(){return"id="+id+"name="+name+"age="+age+"salary="+salary;}publicstaticvoidmain(String[]args){EmployeeemployeesnewEmployee[]{newEmployee(1"张三newEmployee(2"李四2300[0].compareTo(employees[10){System.out.println(employees[0]);System.out.println(employees[1]);}else{System.out.println(employees[1]);System.out.println(employees[0]);}}}⽤compareTo()⽅法计算连个⾯积之差publicpublicclassCircleimplementsComparable<Circle>{doubleradius;publicCircle(doubleradius){this.radius=radius;}publicdoublegetArea(){returnMath.PI*radius*radius;}@OverridepublicintcompareTo(Circlecircle){return(int)(circle.getArea()-getArea());}publicstaticvoidmain(String[]args){Circle[]circles=newCircle[]{newCircle(1.0),newCircle(2.0),newCircle(3.0)};System.out.println(circles[0].compareTo(circles[1]));}}设计⼀个Position类，该类有两个成员变量x,y表⽰坐标。publicpublicclassPositionimplementsComparable<Position>{intx;inty;publicPosition(intx,inty){this.x=x;this.y=y;}@OverridepublicintcompareTo(Positiono){doubledist1=Math.sqrt(x*x+y*y);doubledist2=Math.sqrt(o.x*o.x+o.y*o.y);return(int)(dist1-dist2);}publicstaticvoidmain(String[]args){Positionposition1=newPosition(1,2);Positionposition2=newPosition(2,4);System.out.println(pareTo(position2));}}11.8实现Student对象按姓名排序。importimport

Arrays;Comparator;classCompimplementsComparator<Student>{@Overridepublicintcompare(Studento1,Studento2){if(pareTo()>0){return1;}elseif(pareTo()<0){return-1;}else{return0;}}}publicclassStudentimplementsComparable<Student>{intid;Stringname;publicStudent(intid,Stringname){this.id=id;=name;}@OverridepublicintcompareTo(Studento){returnthis.id-o.id;}publicStringtoString(){return"id="+id+"name="+name;}publicstaticvoidmain(String[]args){StudentstudentnewStudent[]{newStudent(1,""newStudent(2""newStudent(3"".sort(studentnewComp());for(Students:student){System.out.println(s);}}}10.9编写程序，对字符串数组进⾏降序排序。importimportimportArrays;Comparator;publicclassDescSortimplementsComparator<String>{@Overridepublicintcompare(Stringo1,Stringo2){pareTo(o2);}publicstaticvoidmain(String[]args){String[]s=newString[]{"google","baidu","souhu"};Arrays.sort(s,newDescSort());for(Strings1:s){System.out.println(s1);}}10.12使⽤Lambda表达式实现calculate()⽅法。interfaceinterfaceCalculate{public doublecalculate(doublea,doubleb);}publicclassCalculatorDemo{publicstaticvoidmain(String[]args){Calculatec=(a,b)->Math.pow(a,2)+Math.pow(b,2);inta=10;intb=20;System.out.println(c.calculate(a,b));}}第11章泛型与集合11.1publicclasspublicclassPoint<T>{Tx,y;publicPoint(Tx,Ty){this.x=x;this.y=y;}publicvoidsetX(Tx){this.x=x;}publicTgetX(){returnx;}publicvoidsetY(Ty){this.y=y;}publicTgetY(){returny;}publicvoidtranslate(Tx,Ty){this.x=x;this.y=y;}publicStringtoString(){return"x="+x+"y="+y;}publicstaticvoidmain(String[]args){Point<Integer>point1=newPoint<>(1,2);Point<Double>point2=newPoint<>(3.0,4.0);point1.translate(5,6);System.out.println(point1);System.out.println(point2);}}11.4创建⼀个ArrayList对象，在其中添加若⼲元素，编写程序，使⽤3种⽅法将每个字符转换成⼤写。importimportArrayList;Arrays;Iterator;List;publicclassUpperCaseDemo{publicstaticvoidmain(String[]args){List<String>list=newArrayList<>();String[]s={"google","baidu","zijie"};for(inti=0;i<s.length;i++){list.add(s[i]);}for(inti=0;i<list.size();i++){Stringname=list.get(i);name=name.toUpperCase();list.set(i,name);}System.out.println(list);List<String>list1=Arrays.asList(s);Iteratoriterator=list1.iterator();while(iterator.hasNext()){Stringname=(String)iterator.next();name=name.toUpperCase();System.out.print(name+"");}list1.replaceAll(String::toUpperCase);System.out.println(list1);}}importimportHashSetimportimportHashSet;Set;publicclassFindDump{publicstaticvoidmain(String[]args){Strings="IcanIcomeIfly";Set<String>unique=newHashSet<>();Set<String>dump=newHashSet<>();String[]array=s.split("");for(Strings1:array){if(!unique.add(s1)){dump.add(s1);}}System.out.println("dumpSystem.out.println("unique.size.out.println(""+unique);}}11.6编写程序，随机⽣成10个两位整数，将其分别存⼊HashSet和TreeSet对象，然后将他们输⼊，观察输出结果的不同。importimportHashSet;Set;TreeSetpublicclassSetDemo{publicstaticvoidmain(String[]args){Set<Integer>hashSet=newHashSet<>();Set<Integer>treeSet=newTreeSet<>();for(inti=0;i<10;i++){intnum=(int)(Math.random()*10+90);hashSet.add(num);treeSet.add(num);}System.out.println(hashSet);//⽆序不重复System.out.println(treeSet//有序不重复}}11-7编写程序，实现⼀个对象栈类，要求利⽤ArrayList类实现该栈。importimportArrayList;publicclassMyStack<T>{privateArrayList<T>list;publicMyStack(){list=newArrayList<T>();}publicbooleanisEmpty(){returnlist.isEmpty();}publicintgetSize(){returnlist.size()}publicTpeek(){returnlist.get(0);}publicTpop(){returnlist.remove(0);}publicvoidpush(Tt){list.add(0,t);}publicintsearch(Tt){returnlist.indexOf(t);}publicstaticvoidmain(String[]args){MyStack<Integer>list=newMyStack<>();list.push(newInteger(1));list.push(newInteger(2));list.push(newInteger(3));System.out.println(list.getSize());System.out.println(list.isEmpty());System.out.println(list.pop());System.out.println(list.peek());System.out.println(list.search(1));}}假设Employee类包含⼀个int成员id,如果要求Employee可以按id值⽐较⼤⼩，创建⼏个Employee对象，将它们存储到TreeSet中。importimportimportSet;TreeSet;publicclassEmployeeimplementsComparable<Employee>{publicintid;publicStringname;publicEmployee(intid,Stringname){this.id=id;=name;}@OverridepublicintcompareTo(Employeeemployee){returnthis.id-employee.id;}publicStringtoString(){return"id="+id+"name="+name;}publicstaticvoidmain(String[]args){EmployeeemployeesnewEmployee[3newEmployee(1"王国栋newEmployee(3"唐乃乔newEmployee(2"张珂珂[0ts.add(employees[1]);ts.add(employees[2]);for(Employeeemp:ts){System.out.println(emp);}}}编写程序，实现⼀个PriorityQueue对象，将整形数组元素插⼊队列，然后输出并观察结果。importimportimportPriorityQueue;Queue;publicclassPQDemo{publicstaticvoidmain(String[]args){Queue<Integer>queue=newPriorityQueue<>();Integer[]array={1,5,3,7,6,9,8};for(inti=0;i<array.length;i++){queue.add(array[i]);}while(!queue.isEmpty()){System.out.println(queue.poll());}}}编写程序，⽣成⼀个包含1000个随机⽣成的3位数的流，过滤该流，使其仅能包含被7整除或者含有7的数，输出这些数和个数。importimportIntStream;publicclassIntStreamDemo{publicstaticvoidmain(String[]args){int[]nums=newint[1000];for(inti=0;i<nums.length;i++){nums[i]=(int)(Math.random()*900+100);}IntStreamstream=IntStream.of(nums);stream=stream.filter(n->((n%7==0)||(n%10==7)||((n/10)%10==7))||(n/100==7));int[]result=stream.toArray();for(inti=0;i<result.length;i++){System.out.println(result[i]);}System.out.println("满⾜条件的个数："+result.length);}}importBigIntegerimportBigInteger;Duration;Instant;Arrays;List;publicclassParallelStreamDemo{publicstaticBigIntegerfactorial(longn){BigIntegerresult=newBigInteger("1");for(inti=1;i<=n;i++){result=result.multiply(newBigInteger(i+""));}returnresult;}publicstaticvoidmain(String[]args){List<Integer>list=Arrays.asList(10,20,30,40);Instantbegin=Instant.now();list.parallelStream().map(n->(factorial(n))).forEach(System.out::println);Instantend=Instant.now();System.out.println("使⽤并⾏流使⽤时间："+Duration.between(begin,end).toMillis()+"毫秒");Instantbegin1=Instant.now();list.stream().map(n->(factorial(n))).forEach(System.out::println);Instantend1=Instant.now();System.out.println("使⽤顺序流使⽤时间："+Duration.between(begin1,end1).toMillis()+"毫秒");}}第12章异常处理12.1importimportimportInputMismatchException;Scanner;publicclassTest{publicstaticvoidmain(String[]args){try{Scannerinput=newScanner(System.in);System.out.print("请输⼊⼀个double型的圆形半径:");doubleradius=input.nextDouble();System.out.println("Math.PI*radius*radius}catch(InputMismatchExceptione){System.out.println(e);System.out.println("输⼊格式不正确}}}提⽰⽤户输⼊两个整数，然后显⽰它们的和，程序应该在输⼊不正确时，提⽰⽤户再次读取数字。importimportimportInputMismatchException;Scanner;publicclassExceptionDemo{publicstaticvoidmain(String[]args){Scannerinput=newScanner(System.in);booleancontinueInput=true;while(continueInput)try{System.out.print("intainput.nextInt();intb=input.nextInt();intsum=a+b;continueInput=System.out.println("a+b="+sum);}catch(InputMismatchExceptione){System.out.println(e);input.nextLine();}}}⾸先创建⼀个由100个随机选取的整数构成的数组，然后提⽰⽤户输⼊数组下标，程序显⽰对应元素的值，如果输⼊下标越界，则提⽰下标越界。importimportimportRandom;Scanner;publicclassIndexDemo{publicstaticvoidmain(String[]args){Scannerinput=newScanner(System.in);int[]array=newint[100];Randomrandom=newRandom();for(inti=0;i<array.length;i++){array[i]=random.nextInt();}t