javaio流练习题

Ⅰ java iO 流问题

这个可以改成:Scanner sc=new Scanner(System.in);

经过包装后，程序是一行一行读，当读到"end"程序就终止了。br.readLine()，一次读一行。

还有while(len!=-1)的，当读字节时，就不可以用这样的方法了

Ⅱ java题目，io流问题

我这里有一个简单的学生管理系统，你只需要把Student学生类修改成名片类就可以了。你需要新建立一个java文件名为HW4.java,复制粘贴以下代码，编译运行就可以了。

importjava.io.File;
importjava.io.FileInputStream;
importjava.io.FileNotFoundException;
importjava.io.FileOutputStream;
importjava.io.IOException;
importjava.io.ObjectInputStream;
importjava.io.ObjectOutputStream;
importjava.io.Serializable;
importjava.util.Arrays;
importjava.util.Comparator;
importjava.util.Scanner;

<Student>,Serializable{
/**
	*SerializableUID:ensuresserialize/de-.
	*/
	=-3515442620523776933L;

	publicintgetNumber(){
		returnnumber;
	}

	publicvoidsetNumber(intnumber){
		this.number=number;
	}

	publicintgetAge(){
		returnage;
	}

	publicvoidsetAge(intage){
		this.age=age;
	}

	publicdoublegetWeight(){
		returnweight;
	}

	publicvoidsetWeight(doubleweight){
		this.weight=weight;
	}

	publicStringgetName(){
		returnname;
	}

	publicvoidsetName(Stringname){
		this.name=name;
	}

	privateintnumber;
privateintage;
privatedoubleweight;
privateStringname;

publicStudent(intnumber,intage,doubleweight,Stringname){
this.number=number;
this.age=age;
this.weight=weight;
this.name=name;
}

	@Override
	publicintcompareTo(Studento){
		if(this.age==o.age){
			return(int)(this.weight-o.weight);
		}
		returnthis.age-o.age;
	}
}

<Student>{

	@Override
	publicintcompare(Studento1,Studento2){
		returno1.getAge()-o2.getAge();
	}
}

<Student>{

	@Override
	publicintcompare(Studento1,Studento2){
		return(int)(o1.getWeight()-o2.getWeight());
	}
}

publicclassHW4{
	//.
publicstaticvoidmain(String[]args){
System.out.println("
WelcometotheSystem,Chooseoptionsbelow:");
	printPrompt();
	
	Student[]students=null;
Scannerscanner=newScanner(System.in);
while(scanner.hasNextInt()){
switch(scanner.nextInt()){
case1:
	System.out.println("PrintStudentInformation");
	if(students==null){
		System.out.println("PleaseInitiliseNstudentsfirst");
	}else{
		printStudents(students);
	}
	printPrompt();
break;
case2:
System.out.println(":");
intnumber=scanner.nextInt();
students=initilise(number,scanner);
printPrompt();
break;
case3:
	System.out.println("Addanewstudent");
	printPrompt();
	if(students==null){
		System.out.println("PleaseInitiliseNstudentsfirst");
	}else{
		intnewLength=students.length+1;
		students=Arrays.Of(students,newLength);
		students[newLength-1]=createStudent(scanner);
		System.out.println("Newstudenthasbeenadded.");
		printPrompt();
	}
break;
case4:
	System.out.println("SortingbyAge,WeightinAsceorder");
	if(students==null){
		System.out.println("PleaseInitiliseNstudentsfirst");
	}else{
		Student[]sortedStudents=students;
		Arrays.sort(sortedStudents);
		printStudents(sortedStudents);
	}
	break;
case5:
	System.out.println("CalcaulteMin,Max,AveofAgeandWeight");
	if(students==null){
		System.out.println("PleaseInitiliseNstudentsfirst");
	}else{
		Student[]sortedAgeStudents=students;
		Arrays.sort(sortedAgeStudents,newStudentSortByAge());
		Student[]sortedWeightStudents=students;
		Arrays.sort(sortedWeightStudents,newStudentSortByWeight());
		intaverageAge=0;
		doubleaverageWeight=0.0;
		for(Studentstudent:sortedAgeStudents){
			averageAge+=student.getAge();
			averageWeight+=student.getWeight();
		}
		averageAge=averageAge/sortedAgeStudents.length;
		averageWeight=averageWeight/sortedWeightStudents.length;
		System.out.printf("MinAge:%d,MaxAge:%d,AveAge:%d
",sortedAgeStudents[0].getAge(),sortedAgeStudents[sortedAgeStudents.length-1].getAge(),averageAge);
		System.out.printf("MinWeight:%f,MaxWeight:%f,AveWeight:%f
",sortedWeightStudents[0].getWeight(),sortedWeightStudents[sortedWeightStudents.length-1].getWeight(),averageWeight);
	}
	break;
case6:
	System.out.println("WriteStudentdataintofile");
	try(ObjectOutputStreamoos=newObjectOutputStream(newFileOutputStream(newFile("studentsData"),true))){
	oos.writeObject(students);
	printPrompt();
	}catch(FileNotFoundExceptione){
						//TODOAuto-generatedcatchblock
						e.printStackTrace();
					}catch(IOExceptione){
						//TODOAuto-generatedcatchblock
						e.printStackTrace();
					}
	break;
case7:
	System.out.println("ReadstudentDatafromfile");
	try(ObjectInputStreamois=newObjectInputStream(newFileInputStream(newFile("studentsData")))){
		students=(Student[])(ois.readObject());
		printPrompt();
	}catch(FileNotFoundExceptione){
						//TODOAuto-generatedcatchblock
						e.printStackTrace();
					}catch(IOExceptione){
						//TODOAuto-generatedcatchblock
						e.printStackTrace();
					}catch(ClassNotFoundExceptione){
						//TODOAuto-generatedcatchblock
						e.printStackTrace();
					}
	break;
default:
	scanner.close();
	System.out.println("Quit");
break;
}
}
}

publicstaticvoidprintPrompt(){
System.out.println("1:Displaycurrentstudents");
System.out.println("2:InitiliseNstudents");
System.out.println("3:Addnewstudent");
System.out.println("4:SortingbyAge,WeightinAsceorder");
System.out.println("5:CalcaulteMin,Max,AveofAgeandWeight");
System.out.println("6:WriteStudentdataintofile");
System.out.println("7:ReadstudentDatafromfile");
}

publicstaticStudent[]initilise(intn,Scannerscanner){
Student[]students=newStudent[n];
for(inti=0;i<n;i++){
students[i]=createStudent(scanner);
}
System.out.println(".");
returnstudents;
}

publicstaticvoidprintStudents(Student[]students){
	for(Studentstudent:students){
		System.out.printf("Student:%s,Number:%d,Age:%d,Weight:%f
",student.getName(),student.getNumber(),student.getAge(),student.getWeight());
	}
}

(Student[]students){
	for(Studentstudent:students){
		System.out.printf("Age:%d,Weight:%f,Student:%s,Number:%d
",student.getAge(),student.getWeight(),student.getName(),student.getNumber());
	}
}

(Scannerscanner){
intstudentNumber=0,studentAge=0;
doublestudentWeight=0.0;
StringstudentName=null;
System.out.println("EnterStudentNumber:");
while(scanner.hasNext()){
studentNumber=scanner.nextInt();

System.out.println("EnterStudentAge:");
studentAge=scanner.nextInt();

System.out.println("EnterStudentWeight:");
//nextDouble仅仅读取double的值，在double值后的'
'将会被nextLine()所读取，所以读取studentName时需要再读取一次nextLine()
studentWeight=scanner.nextDouble();

System.out.println("EnterStudentName:");
scanner.nextLine();
studentName=scanner.nextLine();
break;
}
returnnewStudent(studentNumber,studentAge,studentWeight,studentName);
}
}