我想删除列表中的第一个元素遭遇
例如
* TestPrelabB.java
*/
import static org.junit.Assert.fail;
import org.junit.Test;
import java.io.PrintStream;
import java.io.ByteArrayOutputStream;
public class TestPrelabB
{
/**
* Check mutators to make sure
* properly.
*/
@Test
public void checkAccessorsMutators001()
{
checkStringAMMonthName("June");
checkStringAMMonthName("July");
checkIntAMDaysInMonth(5);
checkIntAMDaysInMonth(7);
checkIntArrayAMMaxTemperature(new int[]{1, 2});
checkIntArrayAMMaxTemperature(new int[]{3, 4, 5});
}
/**
* Check constructors.
*/
@Test
public void checkConstructors002()
{
checkNoArgConstructor();
check2ArgConstructor("June", 2);
check2ArgConstructor("July", 3);
}
/**
* Make sure setDayMaxTemp functions properly with
* in range data.
*/
@Test
public void checkSetDayMaxTemp003()
{
checkSetDayMaxTemp(2, 85);
checkSetDayMaxTemp(5, 37);
checkSetDayMaxTempMinMax();
checkSetDayMaxTempOOB();
}
/**
* Make sure displayWeatherData prints properly.
*/
@Test
public void checkDisplayWeatherMonth004()
{
String answer1 = "";
answer1 += "June\n";
answer1 += "Day\tMax\n";
answer1 += "1\t-999\n";
answer1 += "2\t-999\n";
String answer2 = "";
answer2 += "June\n";
answer2 += "Day\tMax\tMin\n";
answer2 += "1\t-999\t-999\n";
answer2 += "2\t-999\t-999\n";
checkDisplayWeatherMonth("June", 2, answer1, answer2);
answer1 = "August\n";
answer1 += "Day\tMax\n";
answer1 += "1\t-999\n";
answer1 += "2\t-999\n";
answer1 += "3\t-999\n";
answer2 = "August\n";
answer2 += "Day\tMax\tMin\n";
answer2 += "1\t-999\t-999\n";
answer2 += "2\t-999\t-999\n";
answer2 += "3\t-999\t-999\n";
checkDisplayWeatherMonth("August", 3, answer1, answer2);
}
/**
* Check 2-arg constructor.
* @param monthName The initial name of this WeatherMonth.
* @param daysInMonth The initial number of days in this WeatherMonth.
*/
public void check2ArgConstructor(String monthName,
int daysInMonth)
{
String fb = "";
fb += "Fail in TestPrelabB.\n";
fb += "2-arg constructor is incorrect.\n";
WeatherMonth weatherMonth = new WeatherMonth(monthName,
daysInMonth);
int[] temps = null;
try
{
temps = weatherMonth.getMaxTemperature();
}
catch (NullPointerException e)
{
temps = null;
}
if (!weatherMonth.getMonthName().equals(monthName))
{
fb += "Field monthName was not set correctly.";
fail(fb);
}
else if (temps == null)
{
fb += "Field maxTemperature was left null.";
fail(fb);
}
else if (temps.length != daysInMonth)
{
fb += "Field maxTemperature does not have the ";
fb += "correct length.";
fail(fb);
}
else
{
boolean fail = false;
for (int i = 0; i < temps.length; i++)
{
if (temps[i] != -999)
{
fail = true;
}
}
if (fail)
{
fb += "Not All values in maxTemperature were ";
fb += "initialized to -999.";
fail(fb);
}
}
}
/**
* Check 2-arg constructor.
*/
public void checkNoArgConstructor()
{
String fb = "";
fb += "Fail in TestPrelabB.\n";
fb += "No-arg constructor is incorrect.\n";
WeatherMonth weatherMonth = new WeatherMonth();
int[] temps = null;
try
{
temps = weatherMonth.getMaxTemperature();
}
catch (NullPointerException e)
{
temps = null;
}
if (!weatherMonth.getMonthName().equals("January"))
{
fb += "Field monthName was not set correctly.";
fail(fb);
}
else if (temps == null)
{
fb += "Field maxTemperature was left null.";
fail(fb);
}
else if (temps.length != 31)
{
fb += "Field maxTemperature does not have the ";
fb += "correct length.";
fail(fb);
}
else
{
boolean fail = false;
for (int i = 0; i < temps.length; i++)
{
if (temps[i] != -999)
{
fail = true;
}
}
if (fail)
{
fb += "Not All values in maxTemperature were ";
fb += "initialized to -999.";
fail(fb);
}
}
}
/**
* Check display weather data with data.
*
* Activity 3 requires modification of this method. both answers
* must be allowed here to keep the modifications in activity 3
* from causing a failure here. As long as the answer matches one
* of the two posibilities it is given a pass here.
*
* @param name The name of this WeatherMonth for testing.
* @param days The number of days in this month for testing.
* @param answer1 The correct, expected result of the students output
* after completing the prelab.
* @param answer2 The correct, expected result of the students output
* after the student has completed activity 3.
*/
public void checkDisplayWeatherMonth(String name, int days,
String answer1, String answer2)
{
String fb = "";
fb += "Fail in TestPrelabB.\n";
fb += "Method displayWeatherMonth is incorrect.\n";
String output = captureDisplayWeatherData(name, days);
if (!output.equals(answer1) && !output.equals(answer2))
{
fb += "Your output is not formatted exactly as specified.\n";
fb += "Name of month is " + name + " and number of days\n";
fb += "is " + days + ".\n";
fb += "This is the expected output:\n";
fb += answer1;
fb += "\nThis is your output:\n";
fb += output;
fb += "\nMake sure you printed the month name first.\n";
fb += "Make sure you printed the header line.\n";
fb += "Make sure each line has a number and a temperature.\n";
fb += "Make sure tabs separate data items in each row\n";
fb += "including the header row.\n";
fail(fb);
}
}
/**
* Check the setDayMaxTemp method with data.
* @param day The day to set the given temperature.
* @param temp The temperature to set.
*/
public void checkSetDayMaxTemp(int day, int temp)
{
String fb = "";
fb += "Fail in TestPrelabB.\n";
fb += "Method setDayMaxTemp is incorrect.\n";
WeatherMonth weatherMonth = new WeatherMonth("June",
day + 2);
weatherMonth.setDayMaxTemp(day, temp);
int[] temps = weatherMonth.getMaxTemperature();
//Check all locations EXCEPT for the correct one.
for (int i = 0; i < temps.length; i++)
{
if (i != day - 1)
{
if (temps[i] == temp)
{
fb += "Temperature is stored in the wrong position.\n";
fb += "Ran setDayMaxTemp(" + day + "," + temp + ");\n";
fb += temp + " should have been stored at location ";
fb += (day - 1) + "\n";
fb += temp + " was found at location " + i + ".\n";
fail(fb);
}
}
}
//Check to see if the correct temp is stored at the correct
//location.
if (temps[day - 1] != temp)
{
fb += "Temperature is not stored in the array.\n";
fb += "Ran setDayMaxTemp(" + day + "," + temp + ");\n";
fb += temp + " should have been stored at location ";
fb += (day - 1) + "\n";
fail(fb);
}
}
/**
* Check the setDayMaxTempMinMax method with data.
* This method is here simply because the boundaries were not
* being tested in the prelab test, where it should have been.
*
*/
public void checkSetDayMaxTempMinMax()
{
String fb = "";
fb += "Fail in TestPrelabB.\n";
fb += "Method setDayMaxTemp is incorrect.\n";
WeatherMonth weatherMonth = new WeatherMonth("Test", 31);
weatherMonth.setDayMaxTemp(1, 85);
weatherMonth.setDayMaxTemp(31, 95);
int[] temps = weatherMonth.getMaxTemperature();
//Check to see if the correct temp is stored at the correct
//location.
if (temps[0] != 85)
{
fb += "You did not allow temperature setting on day 1.\n";
fb += "Ran setDayMaxTemp(1, 85);\n";
fb += "85 should have been stored at location 0.\n";
fb += "You had " + temps[0] + " at location 0.\n";
fail(fb);
}
if (temps[30] != 95)
{
fb += "You did not allow temperature setting on last day of month.\n";
fb += "Ran setDayMaxTemp(31, 95); on a month with 31 days.\n";
fb += "95 should have been stored at location 30.\n";
fb += "You had " + temps[30] + " at location 30.\n";
fail(fb);
}
}
/**
* Check the setDayMaxTemp method with out of bounds data.
*/
public void checkSetDayMaxTempOOB()
{
String fb = "";
fb += "Fail in TestPrelabB.\n";
fb += "Method setDayMaxTemp is incorrect.\n";
WeatherMonth weatherMonth = new WeatherMonth("June", 2);
try
{
weatherMonth.setDayMaxTemp(0, 95);
weatherMonth.setDayMaxTemp(3, 95);
weatherMonth.setDayMaxTemp(10, 95);
int[] temps = weatherMonth.getMaxTemperature();
//Check all locations to make sure none changed.
for (int i = 0; i < temps.length; i++)
{
if (temps[i] != -999)
{
fb += "This method should not allow setting of data\n";
fb += "for days less than 1 or days greater than the\n";
fb += "number of days in the month.\n";
fb += "Your method incorrectly changed the temperature\n";
fb += "in the maxTemperature array when given a day\n";
fb += "outside of the allowed range.\n";
fb += "You should ignore out of bounds days.\n";
fail(fb);
}
}
}
catch (IndexOutOfBoundsException e)
{
fb += "This method should not allow setting of data\n";
fb += "for days less than 1 or days greater than the\n";
fb += "number of days in the month.\n";
fb += "Your method attempted to change the temperature\n";
fb += "in the maxTemperature array when given a day\n";
fb += "outside of the allowed range.\n";
fb += "You should ignore out of bounds days.\n";
fail(fb);
}
}
/**
* Check the monthName accessor and mutator with normal valid data.
* @param testData The monthName to set for testing.
*/
public void checkStringAMMonthName(String testData)
{
String fb = "";
fb += "Fail in TestPrelabB.\n";
fb += "Accessor or mutator for monthName field is incorrect.\n";
WeatherMonth weatherMonth = new WeatherMonth("", 1);
weatherMonth.setMonthName(testData + "X");
String setData = weatherMonth.getMonthName();
if (setData == null)
{
fb += "Field is null after setting valid data.";
fail(fb);
}
else if (!setData.equals(testData + "X"))
{
fb += "Field value is incorrect after setting valid data.";
fail(fb);
}
}
/**
* Determine if two int arrays are equal in size
* and each element matches.
* @param a The first array for equality checking.
* @param b The second array for equality checking.
* @return Returns true if a and b are both the same
* length and each element matches.
*/
private boolean intArrayEquals(int[] a, int[] b)
{
if (a == b)
{
return true;
}
else if (a.length != b.length)
{
return false;
}
else
{
//Check each element. Arrays are unequal if even one
//is different.
for (int i = 0; i < a.length; i++)
{
if (a[i] != b[i])
{
return false;
}
}
}
//Same length and all elements are the same.
return true;
}
/**
* Check the monthName accessor and mutator with normal valid data.
* @param testData The monthName to set for testing.
*/
public void checkIntArrayAMMaxTemperature(int[] testData)
{
String fb = "";
fb += "Fail in TestPrelabB.\n";
fb += "Accessor or mutator for maxTemperature field is incorrect.\n";
WeatherMonth weatherMonth = new WeatherMonth("", 1);
weatherMonth.setMaxTemperature(testData);
int[] setData = weatherMonth.getMaxTemperature();
if (setData == null)
{
fb += "Field is null after setting valid data.";
fail(fb);
}
else if (!intArrayEquals(testData, setData))
{
fb += "Field value is incorrect after setting valid data.\n";
fb += "Set array and get array differ in size or\n";
fb += "one or more elements are different.\n";
fail(fb);
}
}
/**
* Check the daysInMonth accessor and mutator with normal valid data.
* @param testData The monthName to set for testing.
*/
public void checkIntAMDaysInMonth(int testData)
{
String fb = "";
fb += "Fail in TestPrelabB.\n";
fb += "Accessor or mutator for daysInMonth field is incorrect.";
int initData = 1;
if (testData == 1)
{
initData = 2;
}
WeatherMonth weatherMonth = new WeatherMonth("", initData);
weatherMonth.setDaysInMonth(testData);
int setData = weatherMonth.getDaysInMonth();
if (setData != testData)
{
fail(fb);
}
}
/**
* Capture student output.
* @param name The name of this WeatherMonth for testing.
* @param days The number of days in this WeatherMonth.
* @return Returns the output of the student output data as an
* array of strings.
*/
public String captureDisplayWeatherData(String name, int days)
{
String fb = "";
//Scanner testInput = new Scanner(testData);
//terminal now prints to the Terminal Window like this
// terminal.println("Hello");
PrintStream terminal = System.out;
//Set up System to print to a byte array
ByteArrayOutputStream output = new ByteArrayOutputStream();
System.setOut(new PrintStream(output));
//Run the students method and capture the results.
WeatherMonth weatherMonth = new WeatherMonth(name, days);
weatherMonth.displayWeatherMonth();
System.out.flush();
//Print user output to terminal
//terminal.println(output);
//Restore printing
System.setOut(terminal);
//Replace all crnl with nl
//Replace all cr with nl
//Only nl should remain
String studentData = output.toString();
studentData = studentData.replaceAll("\r\n", "\n");
studentData = studentData.replaceAll("\r", "\n");
//Split the lines into an array of strings
//return studentData.split("\n");
return studentData;
}
}
但我不知道我的代码中缺少什么，也许我陷入了无限循环
> (remove-first '(10 20 30 40 50 40 30 20 10) 10)
(20 30 40 50 40 30 20 10)
> (remove-first '(10 20 30 40 50 40 30 20 10) 40)
(10 20 30 50 40 30 20 10)
> (remove-first '("A" "B" "C" "d" "e" "F") "d")
("A" "B" "C" "e" "F")
> (remove-first '(10 20 30 40 50 40 30 20 10) 60)
(10 20 30 40 50 40 30 20 10)
> (remove-first (remove-first '(10 20 30 40 50 40 30 20 10) 40) 40)
(10 20 30 50 30 20 10)
答案 0 :(得分：2)
您应该研究用于遍历输入列表和构建输出列表的标准模板作为答案，相同的解决方案结构用于许多问题，并且您的代码当前不遵守它。其他错误包括：
equal?进行比较，因为=仅适用于数字这是一个固定版本：
(define remove-first
(lambda (li val)
(cond ((null? li) '())
((equal? val (car li)) (cdr li))
(else (cons (car li) (remove-first (cdr li) val))))))