20155318Java课堂实践20170510

20155318Java课堂实践20170510

修改教材P98 Score2.java

让执行结果数组填充是自己的学号：提交在IDEA或命令行中运行结查截图，加上学号水印，没学号的不给成绩

代码

public static void main(String[] args)
    {
        int[] scores = new int[10];
        for(int score : scores)
        {
            System.out.printf("%2d",score);
        }
        System.out.println();
        Arrays.fill(scores,20155318);
        for(int score : scores)
        {
            System.out.printf("%9d",score);
        }
    }

截图

在IDEA中以TDD的方式对String类和Arrays类进行学习

• 测试相关方法的正常，错误和边界情况

• String类

  • charAt
  • split

• Arrays类

  • sort
  • binarySearch

代码

码云链接

 package exp2;
 import org.junit.Test;
 import junit.framework.TestCase;
 import junit.framework.TestResult;

 import java.util.Arrays;

 public class MyUtil1Test extends TestCase {
     String s1 = "abcde";
     String s2 = "aaa:bbb:ccc";
     String[] a1 = {"aaa","bbb","ccc"};
     int [] c1 = {2,5,3,4};
     char [] c2 = {'a','b','c','d'};

     @org.junit.Test
        public void testNormal() {
            assertEquals("不及格", MyUtil1.percentage2fivegrade(55));
            assertEquals("及格", MyUtil1.percentage2fivegrade(65));
            assertEquals("中等", MyUtil1.percentage2fivegrade(75));
            assertEquals("良好", MyUtil1.percentage2fivegrade(85));
            assertEquals("优秀", MyUtil1.percentage2fivegrade(95));
        }

        @org.junit.Test
        public void testException() {
            //测试出错情况
            assertEquals("错误", MyUtil1.percentage2fivegrade(-10));
            assertEquals("错误", MyUtil1.percentage2fivegrade(105));

        }

        @org.junit.Test
        public void testBoundary() {
            //测试边界情况
            assertEquals("不及格", MyUtil1.percentage2fivegrade(0));
            assertEquals("及格", MyUtil1.percentage2fivegrade(60));
            assertEquals("中等", MyUtil1.percentage2fivegrade(70));
            assertEquals("良好", MyUtil1.percentage2fivegrade(80));
            assertEquals("优秀", MyUtil1.percentage2fivegrade(90));
            assertEquals("优秀", MyUtil1.percentage2fivegrade(100));

        }
     @Test
     public void charAt() throws Exception {
         assertEquals('a',s1.charAt(0));
         assertEquals('e',s1.charAt(4));
     }

     @Test
     public void split() throws Exception {
         assertEquals(a1,s2.split(":"));
     }

     @Test
     public void sort() throws Exception{
         Arrays.sort(c1);
         assertEquals(5,c1[3]);
     }

     @Test
     public void binarySearch() throws Exception{
         int c;
         c = Arrays.binarySearch(c2,'c');
         assertEquals(2,c);
     }
    }

截图

模拟实现Linux下Sort -t : -k 2的功能。

参考 Sort的实现。提交码云链接和代码运行截图。

代码（码云链接）

   import java.util.*;

   public class MySort1 {
       public static void main(String [] args) {
           String [] toSort = {"aaa:10:1:1",
                               "ccc:30:3:4",
                               "bbb:50:4:5",
                               "ddd:20:5:3",
                               "eee:40:2:20"};

          System.out.println("Before sort:");
          for (String str: toSort)
                      System.out.println(str);

          Arrays.sort(toSort);

          System.out.println("After sort:");
          for( String str : toSort)
              System.out.println(str);
      }
  }

代码

package exam20170510;

/**
 * Created by Administrator on 2017/5/10.
 */
import java.util.*;
import java.lang.*;
public class Mysort {
    public static void main(String[] args) {
        String[] toSort = {"aaa:10:1:1",
                "ccc:30:3:4",
                "bbb:50:4:5",
                "ddd:20:5:3",
                "eee:40:2:20"};

        int [] tmp = new int [toSort.length];
        int val;
        String [] s;

        System.out.println("Before sort:");
        for (String i : toSort) {
            System.out.println(i);

        }

        for(int i = 0; i < toSort.length; i++) {
            s = toSort[i].split(":");
            tmp[i] = Integer.parseInt(s[3]);
        }
        Arrays.sort(tmp);

        System.out.println("After sort:");
        for(int i = 0; i < toSort.length; i++)
            for(int j = 0; j < toSort.length; j++){
                s = toSort[j].split(":");
                val = Integer.parseInt(s[3]);
                if(val == tmp[i]) {
                    System.out.println(toSort[j]);
                }
            }
    }
}

截图