本文提供了多个 Java 输入输出操作的示例代码，包括控制台读取数据、文件操作、数据排序展示等，帮助读者理解 Java IO 的基本用法。
答案：
1.
public class IOtest
{
public static void main(String[]
args) {
Scanner scanner= new Scanner(System.in);
int a[]=new int[3];
int i=0;
//boolean flage =true;
while(i!=3){
a[i]=scanner.nextInt();
i++;
}
scanner.close();
Arrays. sort(a);
System. out.println("最小" +a[0]+"------" +"最大" +a[2]);
}
}
2.
public class IOtest
{
public static void init(String
name,String str)throws Exception {
File file= new File("f:" +File.separator+name);
if(!file.exists()){
file.createNewFile();
DataOutputStream out= new DataOutputStream(new FileOutputStream(file));
out.writeBytes(str);
out.close();
}
}
public static void main(String[]
args) throws Exception{
init("b.txt", "hello
world");
}
}
3.
public class IOtest
{
public static void main(String[]
args) throws Exception{
Scanner scanner= new Scanner(System.in);
int i=0;
java.util.List<String> list= new ArrayList<String>();
while(i!=5){
list.add(scanner.next());
i++;
}
scanner.close();
for(int j=list.size();j>0;j--){
System. out.print(list.get(j-1)+"\t" );
}
}
}
4.
public class IOtest
{
public static void main(String[]
args) throws Exception{
Scanner scanner= new Scanner(System. in);
PrintStream print= new PrintStream( new File("f:" +File.separator +"a.txt" ));
String str=scanner.next();
scanner.close();
String name= null ;
String age= null ;
String s[]= str.split( "[\\|]" );
Map<String, String>map= new HashMap<String,
String>();
for (String
s1:s){
String s2[] =s1.split( "[\\:]" );
for (String
s3:s2){
if (s3.matches("\\d+" )){
age=s3;
} else {
name=s3;
}
map.put(name, age);
}
}
List<Map.Entry<String, String>>ma= new ArrayList<Map.Entry<String,
String>>(map.entrySet());
Collections. sort(ma, new Comparator<Map.Entry<String,
String>>() {
@Override
public int compare(Entry<String,
String> o1,
Entry<String, String> o2) {
if (o1.getValue()!= null&&o2.getValue()!= null&&(Integer. parseInt(o1.getValue())>=Integer. parseInt(o2.getValue()))){
return -1;
} else {
return 1;
}
}
});
System. out .println(ma);
// for(Map.Entry<String, String>m:map.entrySet()){
//
// }
}
}
5.
public class IOtest
{
public static void main(String[]
args) throws Exception{
Scanner scanner= new Scanner(System. in);
//PrintStream print=new PrintStream(new
File("f:"+File.separator+"a.txt"));
boolean Y=true ;
String str= null ;
while (Y){
str+=scanner.next();
System. out .println("是否继续输入" );
String s=scanner.next();
if (s.equalsIgnoreCase("Y" )){
Y= true ;
System. out .println("请继续输入" );
}
if (s.equalsIgnoreCase("N" )){
Y= false ;
System. out .println("退出输入" );
}
}
String name= null ;
String age= null ;
DataOutputStream out= new DataOutputStream( new FileOutputStream(new File("f:" +File. separator+ "a.txt")));
out.writeBytes(str);
out.close();
scanner.close();
String s[]= str.split( "[\\|]" );
Map<String, String>map= new HashMap<String,
String>();
for (String
s1:s){
String s2[] =s1.split( "[\\:]" );
for (String
s3:s2){
if (s3.matches("\\d+" )){
age=s3;
} else {
name=s3;
}
map.put(name, age);
}
}
List<Map.Entry<String, String>>ma= new ArrayList<Map.Entry<String,
String>>(map.entrySet());
Collections. sort(ma, new Comparator<Map.Entry<String,
String>>() {
@Override
public int compare(Entry<String,
String> o1,
Entry<String, String> o2) {
if (o1.getValue()!= null&&o2.getValue()!= null&&(Integer. parseInt(o1.getValue())>=Integer. parseInt(o2.getValue()))){
return -1;
} else {
return 1;
}
}
});
System. out .println(ma);
// for(Map.Entry<String, String>m:map.entrySet()){
//
// }
}
}
6.
public class IOtest
{
public static void main(String[]
args) throws Exception{
System. out .println("请输入一段数字字符串" );
Scanner scanner= new Scanner(System. in);
String str=scanner.next();
scanner.close();
int a=0;//偶数
int b=0;//奇数
int sum=0;
for (int i=0;i<str.length();i++){
sum=str.charAt(i)-48;
if (sum%2==0){
a++;
} else {
b++;
}
}
System. out .println("总数是：" +str.length()+ "
偶数："+a+ " 奇数:"+b);
}
}
7.
public class IOtest
{
public static void main(String[]
args) throws Exception{
System. out .println("请输入用户名" );
Scanner scanner= new Scanner(System. in);
String userName=scanner.next();
System. out .println("请输入密码" );
String password=scanner.next();
while (userName== null||password== null){
if (userName== null){
System. out .println("请输入用户名" );
userName=scanner.next();
}
if (password== null){
System. out .println("请输入密码" );
password=scanner.next();
}
}
int count=0;
while (userName!= null&&password!= null){
if (userName.equals("mldn" )&&password.equals( "hello")){
System. out .println("登陆成功" );
scanner.close();
return ;
} else {
count++;
if (count==3){
System. out .println("连续登陆失败三次，系统推出" );
scanner.close();
return ;
} else {
System. out .println("连续登陆三次失败，则系统退出，您还有" +(3-count)+ "次");
System. out .println("用户名或密码错误，请重新输入：" );
System. out .println("请输入用户名" );
userName=scanner.next();
System. out .println("请输入密码" );
password=scanner.next();
}
}
}
}
}
8.
public class IOtest
{
public static void main(String[]
args) throws Exception{
System. out .println("请输入源文件" );
Scanner scanner= new Scanner(System. in);
String ypath=scanner.next();
System. out .println("请输入目标文件" );
String mbpath=scanner.next();
scanner.close();
OutputStream out= new FileOutputStream( new File(mbpath));
InputStream in= new FileInputStream( new File(ypath));
int temp=0;
while ((temp=in.read())!=-1){
out.write(temp);
}
System. out .println("复制完成" );
out.close();
in.close();
}
}
10.
class Student{
private int id ;
private String name;
private int count ;
public int getId()
{
return id ;
}
public void setId(int id)
{
this .id =
id;
}
public String
getName() {
return name ;
}
public void setName(String
name) {
this .name =
name;
}
public int getCount()
{
return count ;
}
public void setCount( int count)
{
this .count =
count;
}
public Student( int id,
String name, int count) {
this .id =
id;
this .name =
name;
this .count =
count;
}
}
public class IOtest
{
public static void main(String[]
args) throws Exception{
Scanner scanner= new Scanner(System. in);
Student student1= new Student(1,"张三" ,0);
Student student2= new Student(2,"李四" ,0);
Student student3= new Student(3,"王五" ,0);
Student student4= new Student(4,"赵六" ,0);
Student students[]={student1,student2,student3,student4};
for (Student
student:students){
System. out .println(student.getId()+":
"+student.getName()+ " 【"+student.getCount()+ "】" );
}
int a=1;
int num1=0,num2=0,num3=0,num4=0;
while (a!=0){
String str= scanner.next();
if (str.matches("\\d+" )){
a=Integer. parseInt(str);
System. out .println("请输入班长候选人代号(数字0结束)：" +a);
if (a==0){
Map<String,Integer> map= new HashMap<String,Integer>();
for (Student
student:students){
System. out .println(student.getId()+":
"+student.getName()+ " 【"+student.getCount()+ "】" );
map.put(student.getName(), student.getCount());
}
List<Map.Entry<String, Integer>>ma= new ArrayList<Map.Entry<String,
Integer>>(map.entrySet());
Collections. sort(ma, new Comparator<Map.Entry<String,
Integer>>() {
@Override
public int compare(Entry<String,
Integer> o1,
Entry<String, Integer> o2) {
if (o1.getValue()!= null &&o2.getValue()!= null &&o1.getValue()>=o2.getValue()){
return 1;
} else {
return -1;
}
}
});
System.out .println(ma.get(3).getKey()+"同学，最后以" +ma.get(3).getValue()+ "当选班长");
return ;
}
if (a==1){
num1++;
students[a-1].setCount(num1);
}
else if (a==2){
num2++;
students[a-1].setCount(num2);
}
else if (a==3){
num3++;
students[a-1].setCount(num3);
}
else if (a==4){
num4++;
students[a-1].setCount(num4);
} else {
System. out .println("此次选票无效，请输入正确的候选人代号" );
}
} else {
System. out .println("此次选票无效，请输入正确的候选人代号" );
System. out .println("请输入班长候选人代号(数字0结束)：" +str);
}
}
}
}
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