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

 package org.base.practice3;

 import org.junit.Test;

 /**
  * Created with IntelliJ IDEA.
  * User: cutter.li
  * Date: 14-3-10
  * Time: 上午10:14
  * java基础练习题第三章
  */
 public class PractiseTest {

     @Test
     public void exercise1() {
         char x = '你', y = 'e', z = '吃';

         if (x > 'A') {
             y = '爱';
             z = '情';
         } else {
             y = '我';
         }
         z = '她';
         System.out.println(" " + x + y + z);

     }

     @Test
     public void exercise2() {
         char c = '\0';
         for (int i = 1; i <= 4; i++) {
             switch (i) {
                 case 1:
                     c = 'b';
                     System.out.print(c);
                 case 2:
                     c = 'e';
                     System.out.print(c);
                     break;
                 case 3:
                     c = 'p';
                     System.out.print(c);
                 default:
                     System.out.print("!");
             }
         }
     }

     //编写一个程序求1！+2！+3！+...+10！
     @Test
     public void exercise3() {

         int sum = 0;

         for (int i = 1; i <= 10; i++) {
             int factorial = 1;
             for (int k = 1; k <= i; k++) {
                 factorial *= k;
             }
             System.out.println(i + "的阶乘是：" + factorial);
             sum += factorial;
         }
         System.out.println("**********************1到10的阶乘之和是：" + sum);
     }

     //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。）
     @Test
     public void exercise4() {

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

             boolean isPrime = true;
             for (int k = 2; k <= i; k++) {
                 if (i % k == 0 && i != k) {
                     isPrime = false;
                     break;
                 } else {
                     continue;
                 }

             }
             if (isPrime && i > 1) {
                 System.out.print(i + " , ");
             }
         }
     }

     //分别用do-while和for计算出1+1/2!+1/3!+...的前20项之和
     @Test
     public void exercise5() {
         int i = 1;
         float sum = 0;
         do {
             int factorial = 1;
             for (int k = 1; k <= i; k++) {
                 factorial *= k;
             }
             sum += (float) 1 / factorial;
             i++;
         } while (i <= 20);
         System.out.println("do-while方法计算的前20项的和是：" + sum);

         float he = 0;
         for (int j = 1; j <= 20; j++) {
             int jiecheng = 1;
             for (int m = 1; m <= j; m++) {
                 jiecheng *= m;
             }
             he += (float) 1 / jiecheng;
         }
         System.out.println("for方法计算的前20项的和是：" + he);
     }

     //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）
     @Test
     public void exercise6() {

         for (int i = 1; i <= 1000; i++) {
             int sum = 0;
             for (int k = 1; k <= i; k++) {
                 if (i % k == 0 && k < i) {
                     sum += k;
                 }
             }
             if (sum == i) {
                 System.out.print(i + " , ");
             }
         }
     }

     //分别使用while和for计算出8+88+888+...前10项的和
     @Test
     public void exercise7() {

         int sum = 0;

         for (int i = 1; i <= 10; i++) {
             int num = 0;
             for (int k = 1; k <= i; k++) {
                 num += Math.pow(10, k - 1);

             }
             System.out.println("第" + i + "的值是：" + num);
             sum += 8 * num;
         }

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

     //计算出1+2+3+...+n<8888 的最大正整数n
     @Test
     public void exercise8() {

         int sum = 0;
         for (int i = 1; i <= Integer.MAX_VALUE; i++) {
             sum += i;
             if (sum >= 8888) {
                 System.out.println("最大的整数是：" + (i - 1));
                 break;
             }
         }

     }

 }

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

 package org.base.practice6;

 import org.junit.Test;

 import java.math.BigInteger;
 import java.text.SimpleDateFormat;
 import java.util.Calendar;
 import java.util.Date;

 /**
  * Created with IntelliJ IDEA.
  * User: cutter.li
  * Date: 14-3-10
  * Time: 下午12:00
  * java基础知识第六章练习题
  */
 public class PractiseTest {

     //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
     @Test
     public void exercise1() {

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

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

     }

     //输入2006年2月的日历页面，程序要处理闰年的问题
     @Test
     public void exercise2() {

         Calendar calendar = Calendar.getInstance();
         calendar.set(2006, 2, 1);

         int year = calendar.get(Calendar.YEAR);
         System.out.println(year + "年" + Calendar.MONTH + "月");
         System.out.println("日 一 二 三 四 五 六");

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

         int dayOfMonth = 28;
         if (year % 400 == 0 || (year % 4 == 0 && year % 100 > 0)) {
             dayOfMonth = 29;
         }
         int week = calendar.get(Calendar.DAY_OF_WEEK);
         for (int k = 1; k < week; k++) {
             System.out.print("*  ");
         }
         for (int i = 1; i <= dayOfMonth; i++) {

             System.out.print(i + "  ");
             if (week % 7 == 0) {
                 System.out.println();
             }
             week++;

         }

     }
     @Test
     public void exercise3() {

         Calendar calendar1=Calendar.getInstance();
         calendar1.set(1988,1,2);

         Calendar calendar2=Calendar.getInstance();
        calendar2.setTime(new Date());

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

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

     }

     @Test
     public void exercise4() {
           System.out.println(Math.nextUp(100f));
     }
     @Test
     public void exercise5() {

         BigInteger sum = BigInteger.ZERO;
         for (BigInteger i = new BigInteger("1", 10); i.intValue() <= 30; i=i.add(new BigInteger("1"))) {
             BigInteger factorial = new BigInteger("1");
             for (BigInteger k = new BigInteger("1"); k.intValue() <= i.intValue();k= k.add(new BigInteger("1"))) {
                 factorial = factorial.multiply(k);
             }
             System.out.println(i+"的阶乘是：" + factorial);
             sum = sum.add(factorial);
         }
         System.out.println("1!+2!+...+30!的和是：" + sum);

     }

 }

3,对字符串的一些练习

 package org.base.practice5;

 import org.junit.Test;

 import java.util.Arrays;

 /**
  * Created with IntelliJ IDEA.
  * User: cutter.li
  * Date: 14-3-10
  * Time: 下午2:33
  * 字符串相关练习题
  */
 public class PractiseTest {

     @Test
     public void exercise1()
     {
         String str="I am a 7Road employee !";

         System.out.println(str);

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

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

     }

     @Test
     public void exercise2()
     {
         String str="cutter GG :".concat("do u want to find a job ?");

         System.out.println(str);

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

     }

     @Test
     public void exercise3()
     {
        String str="中国科学技术大学";
         char a=str.charAt(2),b=str.charAt(6);

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

     @Test
     public void exercise4()
     {
        int a[]={465,2,7979,12,9,3,9655,-10};

         Arrays.sort(a);

         for(int i:a)
         {
             System.out.print(i+" , ");
         }

         System.out.println();
         int b[]= Arrays.copyOf(a,20);

         for(int i:b)
         {
             System.out.print(i + " , ");
         }
     }

     @Test
     public void exercise5()
     {
         Object[] a=new Object[10];
        System.arraycopy(new Object[]{"a",0,"cdef",'f'},0,a,0,2);

         for(Object i:a)
         {
             System.out.print(i + " , ");
         }
     }
 }

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···