Java设计实践课练习题

 1 package hello;
 2 import java.util.*;
 3 
 4 public class Hello {
 5     public static void main(String args[]){
 6         double[] a = produce(10000);
 7         int[] b = tongJi(a);
 8         for (int e : b) {
 9             System.out.print(e +" ");
10         }
11         System.out.println();
12         double exp = expect(a);
13         System.out.println(exp);
14         double f = fangCha(exp, a);
15         System.out.println(f);
16         
17     }
18     public static double[] produce(int length) {
19         double[] a = new double[length];
20         for (int i = 0; i < length; i++) {
21             a[i] = Math.random() * 2 - 1;
22         }
23         return a;
24     }
25     public static int[] tongJi(double a[]) {
26         int[] b = new int[20];
27         for (int i = 0; i < a.length; i++) {
28             for (int j = 0; j < b.length; j++) {
29                 if (a[i] > -1 + 0.1 * j && a[i] < -1 + 0.1 * (j + 1)) {
30                     b[j]++;
31                 }
32             }
33         }
34         return b;
35     }
36     public static double expect(double b[]) {
37         double sum = 0;
38         for (int i = 0; i < b.length; i++) {
39             sum = sum + b[i];
40         }
41         double exp = sum/10000;
42         return exp;
43     }
44     public static double fangCha(double exp, double a[]) {
45         double sum = 0;
46         for (int i = 0; i < a.length; i++) {
47             sum = sum + (a[i] - exp) * (a[i] - exp);
48         }
49         double f = Math.sqrt(sum/10000);
50         return f;
51     }
52 }

View Code

 1 package hello;
 2 import java.util.*;
 3 
 4 public class Hello {
 5     public static void main(String args[]){
 6         double[] a = produce(10000);
 7         int[] b = tongJi(a);
 8         for (int e : b) {
 9             System.out.print(e +" ");
10         }
11         System.out.println();
12         double exp = expect(a);
13         System.out.println(exp);
14         double f = fangCha(exp, a);
15         System.out.println(f);
16         
17     }
18     public static double[] produce(int length) {
19         double[] a = new double[length];
20         for (int i = 0; i < length; i++) {
21             a[i] = getNumRandom();
22         }
23         return a;
24     }
25     public static int[] tongJi(double a[]) {
26         int[] b = new int[20];
27         for (int i = 0; i < a.length; i++) {
28             for (int j = 0; j < b.length; j++) {
29                 if (a[i] > -6 + 0.6 * j && a[i] < -6 + 0.6 * (j + 1)) {
30                     b[j]++;
31                 }
32             }
33         }
34         return b;
35     }
36     public static double expect(double b[]) {
37         double sum = 0;
38         for (int i = 0; i < b.length; i++) {
39             sum = sum + b[i];
40         }
41         double exp = sum/10000;
42         return exp;
43     }
44     public static double fangCha(double exp, double a[]) {
45         double sum = 0;
46         for (int i = 0; i < a.length; i++) {
47             sum = sum + (a[i] - exp) * (a[i] - exp);
48         }
49         double f = Math.sqrt(sum/10000);
50         return f;
51     }
52     public static double getNumRandom() {
53         double sum = 0;
54         for (int i = 0 ; i < 12; i++) {
55             sum = sum + Math.random();
56         }
57         return sum - 6;
58     }
59 }

View Code

 1 import java.util.Scanner;
 2 
 3 /**
 4  * Created by 木子月月鸟 on 2017/5/24.
 5  */
 6 public class Test {
 7     public static void main(String[] args) {
 8         System.out.println("请输入第一个字符串数组：");
 9         Scanner input = new Scanner(System.in);
10         String s1 = input.nextLine();
11         System.out.println("请输入第二个字符串数组：");
12         String s2 = input.nextLine();
13         System.out.println("比较结果为："+compareMinus(s1, s2));
14     }
15     public static boolean compareMinus(String s1, String s2) {
16         boolean flag = true;
17         for (int i = 0; i < s1.length(); i++) {
18             char ch = s1.charAt(i);
19             if (ch == '-') {
20                 if (s2.charAt(i) != '-') {
21                     flag = false;
22                 }
23             }
24         }
25         return flag;
26     }
27 }

View Code

Java文件操作：

①文件删除与创建，文件存在则删除，不存在则创建

 1 import java.io.*;
 2 import java.util.*;
 3 
 4 /**
 5  * Created by 木子月月鸟 on 2017/5/24.
 6  */
 7 public class Test {
 8     public static void main(String[] args) {
 9         File file = new File("C:\Users\木子月月鸟\Desktop\file.txt");
10         if (file.exists()) {
11             file.delete();
12             System.out.println("文件已经删除");
13         } else {
14             try {
15                 file.createNewFile();
16                 System.out.println("文件已经创建");
17             } catch (Exception e) {
18                 e.printStackTrace();
19             }
20         }
21     }
22 }

View Code

②获取文件信息，名字，长度，是否隐藏等

 1 import java.io.*;
 2 import java.util.*;
 3 
 4 /**
 5  * Created by 木子月月鸟 on 2017/5/24.
 6  */
 7 public class Test {
 8     public static void main(String[] args) {
 9         File file = new File("C:\Users\木子月月鸟\Desktop\file.txt");
10         if (file.exists()) {
11             String name = file.getName();
12             long length = file.length();
13             boolean hidden = file.isHidden();
14             System.out.println("文件名称是："+ name);
15             System.out.println("文件长度是："+ length);
16             System.out.println("该文件是隐藏文件么？"+ hidden);
17         } else {
18             System.out.println("该文件不存在！");
19         }
20     }
21 }

View Code

③用FileInputStream和FileOutputStream对文件进行读写操作

 1 import java.io.*;
 2 import java.util.*;
 3 
 4 /**
 5  * Created by 木子月月鸟 on 2017/5/24.
 6  */
 7 public class Test {
 8     public static void main(String[] args) {
 9         File file = new File("C:\Users\木子月月鸟\Desktop\file.txt");
10         try {
11             FileOutputStream out = new FileOutputStream(file);
12             byte[] buy = "我有一只小毛驴，我从来也不骑".getBytes();
13             out.write(buy);
14             out.close();
15         } catch (Exception e) {
16             e.printStackTrace();
17         }
18         try {
19             FileInputStream in = new FileInputStream(file);
20             byte[] by = new byte[1024];
21             int len = in.read(by);
22             System.out.println("文件中的信息是: "+new String(by, 0 ,len));
23             in.close();
24         } catch (Exception e) {
25             e.printStackTrace();
26         }
27     }
28 }

View Code

④用FileReader、FileWriter、BufferedReader、BufferedWriter对文件进行读写操作

 1 import java.io.*;
 2 import java.util.*;
 3 
 4 /**
 5  * Created by 木子月月鸟 on 2017/5/24.
 6  */
 7 public class Test {
 8     public static void main(String[] args) {
 9         File file = new File("C:\Users\木子月月鸟\Desktop\file.txt");
10         String content[] = {"好久不见","最近好吗","常常联系"};
11         try {
12             FileWriter fileWriter = new FileWriter(file);
13             BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);
14             for (int i = 0; i < content.length; i++) {
15                 bufferedWriter.write(content[i]);
16                 bufferedWriter.newLine();
17             }
18             bufferedWriter.close();
19             fileWriter.close();
20         } catch (Exception e) {
21             e.printStackTrace();
22         }
23         try {
24             FileReader fileReader = new FileReader(file);
25             BufferedReader bufferedReader = new BufferedReader(fileReader);
26             String string = null;
27             int i = 0;
28             while ((string = bufferedReader.readLine()) != null) {
29                 i++;
30                 System.out.println("第"+ i + "行:" + string);
31             }
32             bufferedReader.close();
33             fileReader.close();
34         } catch (Exception e) {
35             e.printStackTrace();
36         }
37 
38     }
39 }

View Code

⑤用FileReader、FileWriter、BufferedReader、BufferedWriter对文件复制

 1 import java.io.*;
 2 import java.util.*;
 3 
 4 /**
 5  * Created by 木子月月鸟 on 2017/5/24.
 6  */
 7 public class Test {
 8     public static void main(String[] args) {
 9         File source = new File("C:\Users\木子月月鸟\Desktop\source.txt");
10         File target = new File("C:\Users\木子月月鸟\Desktop\target.txt");
11         try {
12             FileReader fileReader = new FileReader(source);
13             FileWriter fileWriter = new FileWriter(target);
14             BufferedReader bufferedReader = new BufferedReader(fileReader);
15             BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);
16             String string = null;
17             while ((string = bufferedReader.readLine()) != null) {
18                 System.out.println(string);
19                 bufferedWriter.write(string);
20                 bufferedWriter.newLine();
21             }
22             bufferedReader.close();
23             fileReader.close();
24             bufferedWriter.close();
25             fileWriter.close();
26         } catch (Exception e) {
27             e.printStackTrace();
28         }
29     }
30 }

View Code

⑥文件压缩操作

 1 import java.io.*;
 2 import java.util.*;
 3 import java.util.zip.ZipEntry;
 4 import java.util.zip.ZipOutputStream;
 5 
 6 /**
 7  * Created by 木子月月鸟 on 2017/5/24.
 8  */
 9 public class Test {
10     public static void main(String[] args) {
11         Test test = new Test();
12         try {
13             test.zip("C:\Users\木子月月鸟\Desktop\test.zip", new File("C:\Users\木子月月鸟\Desktop\test"));
14             System.out.println("压缩完成!");
15         }catch (Exception e) {
16         }
17     }
18     private void zip(String zipFileName, File inputFile) throws Exception {
19         ZipOutputStream out = new ZipOutputStream(new FileOutputStream(zipFileName));
20         zip(out, inputFile, "");
21         System.out.println("文件压缩中.....");
22         out.close();
23     }
24     private void zip(ZipOutputStream out, File file, String base) throws Exception {
25         if (file.isDirectory()) {
26             File[] files = file.listFiles();
27             out.putNextEntry(new ZipEntry(base + "/"));
28             base = base.length() == 0 ? "" : base + "/";
29             for (int i = 0; i < files.length; i++) {
30                 zip(out, files[i], base + files[i]);
31             }
32         } else {
33             out.putNextEntry(new ZipEntry(base));
34             FileInputStream in = new FileInputStream(file);
35             int b;
36             System.out.println(base);
37             while ((b = in.read()) != -1) {
38                 out.write(b);
39             }
40             in.close();
41         }
42     }
43 }

View Code

（7）文件解压缩操作

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原文地址：https://www.cnblogs.com/muziyueyueniao/p/6897833.html