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 = '';
        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···