java基础练习 字符串，控制流，日历，日期等

1，对基本控制流程的一些练习

  1 package org.base.practice3;

  2 

  3 import org.junit.Test;

  4 

  5 /**

  6  * Created with IntelliJ IDEA.

  7  * User: cutter.li

  8  * Date: 14-3-10

  9  * Time: 上午10:14

 10  * java基础练习题第三章

 11  */

 12 public class PractiseTest {

 13 

 14 

 15     @Test

 16     public void exercise1() {

 17         char x = '你', y = 'e', z = '吃';

 18 

 19         if (x > 'A') {

 20             y = '爱';

 21             z = '情';

 22         } else {

 23             y = '我';

 24         }

 25         z = '她';

 26         System.out.println(" " + x + y + z);

 27 

 28     }

 29 

 30     @Test

 31     public void exercise2() {

 32         char c = '\0';

 33         for (int i = 1; i <= 4; i++) {

 34             switch (i) {

 35                 case 1:

 36                     c = 'b';

 37                     System.out.print(c);

 38                 case 2:

 39                     c = 'e';

 40                     System.out.print(c);

 41                     break;

 42                 case 3:

 43                     c = 'p';

 44                     System.out.print(c);

 45                 default:

 46                     System.out.print("!");

 47             }

 48         }

 49     }

 50 

 51     //编写一个程序求1！+2！+3！+...+10！

 52     @Test

 53     public void exercise3() {

 54 

 55         int sum = 0;

 56 

 57         for (int i = 1; i <= 10; i++) {

 58             int factorial = 1;

 59             for (int k = 1; k <= i; k++) {

 60                 factorial *= k;

 61             }

 62             System.out.println(i + "的阶乘是：" + factorial);

 63             sum += factorial;

 64         }

 65         System.out.println("**********************1到10的阶乘之和是：" + sum);

 66     }

 67 

 68     //求100以内的素数（素数指在大于1的自然数中，除了1和此整数自身外，无法被其他自然数整除的数。）

 69     @Test

 70     public void exercise4() {

 71 

 72         for (int i = 1; i <= 100; i++) {

 73 

 74             boolean isPrime = true;

 75             for (int k = 2; k <= i; k++) {

 76                 if (i % k == 0 && i != k) {

 77                     isPrime = false;

 78                     break;

 79                 } else {

 80                     continue;

 81                 }

 82 

 83             }

 84             if (isPrime && i > 1) {

 85                 System.out.print(i + " , ");

 86             }

 87         }

 88     }

 89 

 90     //分别用do-while和for计算出1+1/2!+1/3!+...的前20项之和

 91     @Test

 92     public void exercise5() {

 93         int i = 1;

 94         float sum = 0;

 95         do {

 96             int factorial = 1;

 97             for (int k = 1; k <= i; k++) {

 98                 factorial *= k;

 99             }

100             sum += (float) 1 / factorial;

101             i++;

102         } while (i <= 20);

103         System.out.println("do-while方法计算的前20项的和是：" + sum);

104 

105 

106         float he = 0;

107         for (int j = 1; j <= 20; j++) {

108             int jiecheng = 1;

109             for (int m = 1; m <= j; m++) {

110                 jiecheng *= m;

111             }

112             he += (float) 1 / jiecheng;

113         }

114         System.out.println("for方法计算的前20项的和是：" + he);

115     }

116 

117     //求1000以内的完数（一个数如果恰好等于他的除了本身之外的所有因子数之和，这个数称为完数）

118     @Test

119     public void exercise6() {

120 

121         for (int i = 1; i <= 1000; i++) {

122             int sum = 0;

123             for (int k = 1; k <= i; k++) {

124                 if (i % k == 0 && k < i) {

125                     sum += k;

126                 }

127             }

128             if (sum == i) {

129                 System.out.print(i + " , ");

130             }

131         }

132     }

133 

134     //分别使用while和for计算出8+88+888+...前10项的和

135     @Test

136     public void exercise7() {

137 

138         int sum = 0;

139 

140         for (int i = 1; i <= 10; i++) {

141             int num = 0;

142             for (int k = 1; k <= i; k++) {

143                 num += Math.pow(10, k - 1);

144 

145             }

146             System.out.println("第" + i + "的值是：" + num);

147             sum += 8 * num;

148         }

149 

150         System.out.println("前10项的和是：" + sum);

151     }

152 

153     //计算出1+2+3+...+n<8888 的最大正整数n

154     @Test

155     public void exercise8() {

156 

157         int sum = 0;

158         for (int i = 1; i <= Integer.MAX_VALUE; i++) {

159             sum += i;

160             if (sum >= 8888) {

161                 System.out.println("最大的整数是：" + (i - 1));

162                 break;

163             }

164         }

165 

166     }

167 

168 }

 

2，对基本类工具Date,Calendar,BigInterger，Math的练习

  1 package org.base.practice6;

  2 

  3 import org.junit.Test;

  4 

  5 import java.math.BigInteger;

  6 import java.text.SimpleDateFormat;

  7 import java.util.Calendar;

  8 import java.util.Date;

  9 

 10 /**

 11  * Created with IntelliJ IDEA.

 12  * User: cutter.li

 13  * Date: 14-3-10

 14  * Time: 下午12:00

 15  * java基础知识第六章练习题

 16  */

 17 public class PractiseTest {

 18 

 19     //用date的不带参数的构造函数创建日期，输出格式为 星期 小时 分 秒

 20     @Test

 21     public void exercise1() {

 22 

 23         Date now = new Date();

 24         String nowStr = new SimpleDateFormat("E HH mm ss").format(now);

 25 

 26         System.out.println("当前的时间：" + nowStr);

 27 

 28 

 29     }

 30 

 31     //输入2006年2月的日历页面，程序要处理闰年的问题

 32     @Test

 33     public void exercise2() {

 34 

 35         Calendar calendar = Calendar.getInstance();

 36         calendar.set(2006, 2, 1);

 37 

 38         int year = calendar.get(Calendar.YEAR);

 39         System.out.println(year + "年" + Calendar.MONTH + "月");

 40         System.out.println("日 一 二 三 四 五 六");

 41 

 42         int weeks = calendar.get(Calendar.DAY_OF_WEEK);

 43 

 44         int dayOfMonth = 28;

 45         if (year % 400 == 0 || (year % 4 == 0 && year % 100 > 0)) {

 46             dayOfMonth = 29;

 47         }

 48         int week = calendar.get(Calendar.DAY_OF_WEEK);

 49         for (int k = 1; k < week; k++) {

 50             System.out.print("*  ");

 51         }

 52         for (int i = 1; i <= dayOfMonth; i++) {

 53 

 54             System.out.print(i + "  ");

 55             if (week % 7 == 0) {

 56                 System.out.println();

 57             }

 58             week++;

 59 

 60         }

 61 

 62     }

 63     @Test

 64     public void exercise3() {

 65 

 66         Calendar calendar1=Calendar.getInstance();

 67         calendar1.set(1988,1,2);

 68 

 69         Calendar calendar2=Calendar.getInstance();

 70        calendar2.setTime(new Date());

 71 

 72         long days= calendar2.getTimeInMillis()-calendar1.getTimeInMillis();

 73 

 74         System.out.println("我活了"+days/(24*60*60*1000)+"天");

 75 

 76 

 77     }

 78 

 79     @Test

 80     public void exercise4() {

 81           System.out.println(Math.nextUp(100f));

 82     }

 83     @Test

 84     public void exercise5() {

 85 

 86         BigInteger sum = BigInteger.ZERO;

 87         for (BigInteger i = new BigInteger("1", 10); i.intValue() <= 30; i=i.add(new BigInteger("1"))) {

 88             BigInteger factorial = new BigInteger("1");

 89             for (BigInteger k = new BigInteger("1"); k.intValue() <= i.intValue();k= k.add(new BigInteger("1"))) {

 90                 factorial = factorial.multiply(k);

 91             }

 92             System.out.println(i+"的阶乘是：" + factorial);

 93             sum = sum.add(factorial);

 94         }

 95         System.out.println("1!+2!+...+30!的和是：" + sum);

 96 

 97 

 98     }

 99 

100 }

View Code

 

3,对字符串的一些练习

 1 package org.base.practice5;

 2 

 3 import org.junit.Test;

 4 

 5 import java.util.Arrays;

 6 

 7 /**

 8  * Created with IntelliJ IDEA.

 9  * User: cutter.li

10  * Date: 14-3-10

11  * Time: 下午2:33

12  * 字符串相关练习题

13  */

14 public class PractiseTest {

15 

16     @Test

17     public void exercise1()

18     {

19         String str="I am a 7Road employee !";

20 

21         System.out.println(str);

22 

23         System.out.println(str.toLowerCase());

24 

25         System.out.println(str.toUpperCase());

26 

27     }

28 

29     @Test

30     public void exercise2()

31     {

32         String str="cutter GG :".concat("do u want to find a job ?");

33 

34         System.out.println(str);

35 

36         System.out.println(29&51+((29^51)>>1));

37 

38 

39     }

40 

41     @Test

42     public void exercise3()

43     {

44        String str="中国科学技术大学";

45         char a=str.charAt(2),b=str.charAt(6);

46 

47         System.out.println(a+" , "+b);

48     }

49 

50     @Test

51     public void exercise4()

52     {

53        int a[]={465,2,7979,12,9,3,9655,-10};

54 

55         Arrays.sort(a);

56 

57         for(int i:a)

58         {

59             System.out.print(i+" , ");

60         }

61 

62         System.out.println();

63         int b[]= Arrays.copyOf(a,20);

64 

65         for(int i:b)

66         {

67             System.out.print(i + " , ");

68         }

69     }

70 

71 

72     @Test

73     public void exercise5()

74     {

75         Object[] a=new Object[10];

76        System.arraycopy(new Object[]{"a",0,"cdef",'f'},0,a,0,2);

77 

78         for(Object i:a)

79         {

80             System.out.print(i + " , ");

81         }

82     }

83 }

 

以上练习使用的是junit4.11,为求简单，使用的是命令行输出，为了复习基本的java知识，特找了java2使用教程的练习来练手，看一遍书，温故而知新···