我正在努力尋找相關的答案來解決我的問題。我有一個數組列表：List<Teacher> teacherList = new ArrayList<Teacher>(11);教師類有一個 name 屬性。我想掃描教師列表，并找出是否有與用戶輸入的名稱匹配的名稱。例如，Scanner teacherNameScanner = new Scanner (System.in);System.out.println("What is the teachers name");teacherName = teacherNameScanner.nextLine();/* Here I want to scan through the teacherList and see whether the name enteredmatches the name of any of the teachers. If it does not match I want to tell theuser to enter a correct name */
3 回答
海綿寶寶撒
TA貢獻1809條經驗 獲得超8個贊
在Java8 中，您可以使用流：
public static Teacher findByName(Collection<Teacher> teachers, String name) {
return teachers.stream().filter(teacher -> teacher.getName().equals(name)).findFirst().orElse(null);
}
此外，如果您有許多不同的對象（不僅是Teacher），或者您想通過不同的屬性（不僅是name）找到它，您可以構建一個實用程序類，以在其中封裝此邏輯：
public final class FindUtils {
public static <T> T findByProperty(Collection<T> col, Predicate<T> filter) {
return col.stream().filter(filter).findFirst().orElse(null);
}
}
public final class TeacherUtils {
public static Teacher findByName(Collection<Teacher> teachers, String name) {
return FindUtils.findByProperty(teachers, teacher -> teacher.getName().equals(name));
}
public static Teacher findByAge(Collection<Teacher> teachers, int age) {
return FindUtils.findByProperty(teachers, teacher -> teacher.getAge() == age);
}
}
慕容森
TA貢獻1853條經驗 獲得超18個贊
這真的取決于您的用例，名稱是否區分大小寫？此外，您可能需要考慮修剪空間。然后創建一個 Set nameSet，您可以在其中對現有名稱進行獲取，這是一個 O(1) 操作。同樣，對此有許多解決方案，除非您描述確切的用例，例如您想用姓名還是 ID（通常是 ID）來識別教師，否則很難想出正確的解決方案。但是根據您所描述的 HashSet 應該可以。
Set<String> nameSet = new HashSet<String>();
if (nameSet.contains(teacherName))
do what you want
else
other case
慕桂英4014372
TA貢獻1871條經驗 獲得超13個贊
要掃描teacherList并查找輸入的教師姓名 ( teacherName)是否匹配，可以使用以下方法之一。請注意，每個方法都將 theteacherList和 theenteredName作為參數并返回booleantrue 或 false - 取決于是否找到匹配項。
共有三種方法，每種方法的表現各不相同。請注意第三個構造 C - 這使用了與前兩個不同的方法 - A 和 B。
方法一：
teacherList使用 for 循環迭代并查找是否有匹配名稱的老師：
for (Teacher teacher : teacherList) {
if (teacher.getName().equals(enteredName)) {
// a match is found
return true;
}
}
return false;
方法B：
這與方法 A 具有相同的功能，但使用不同的代碼構造 - 流和 lambda：
boolean enteredTeacherExists = teacherList.stream()
.anyMatch(teacher -> teacher.getName().equals(enteredName));
語法teacher -> teacher.getName().equals(enteredName)是一個類型為 的 lambda 表達式Predicate<Teacher>。
方法C：
此方法使用不同的方法。不是測試教師的姓名 - 使用輸入的姓名構造教師對象，該對象用于查找匹配項。
根據輸入的名字創建一個教師，并測試它是否存在于列表中。
Teacher enteredTeacher = new Teacher(enteredName);
boolean enteredTeacherExists = teacherList.contains(enteredTeacher);
如果列表中存在同名教師，則返回值為真，否則為假。
請注意Teacher該類（參見下面的定義）有一個java.lang.Object類的重寫equals()方法。此方法指定兩個教師對象相等的標準 - 如果它們的名稱相等，則教師對象被視為相等。這允許使用 equalsList的contains方法。
編碼：
老師.java：
public class Teacher {
private String name;
public Teacher(String name) {
this.name = name;
}
public String getName() {
return name;
}
@Override
/* This returns a string representation of the teacher - the name. */
public String toString() {
return name;
}
@Override
public boolean equals(Object other) {
if ((other != null) && (other instanceof Teacher)) {
Teacher otherTeacher = (Teacher) other;
if (otherTeacher.getName().equals(this.name)) {
return true;
}
}
return false;
}
}
教師測試器.java
public class TeacherTester {
public static void main(String [] args) {
// Create some teachers
Teacher teacher1 = new Teacher("first");
Teacher teacher2 = new Teacher("second");
Teacher teacher3 = new Teacher("third");
List<Teacher> teacherList = Arrays.asList(teacher1, teacher2, teacher3);
System.out.println("Teachers: " + teacherList);
// Look for teacher - using method A
String enteredName = "ninth";
System.out.println("A. Found " + enteredName + " : " + findTeacherA(teacherList, enteredName));
enteredName = "first";
System.out.println("A. Found " + enteredName + " : " + findTeacherA(teacherList, enteredName));
// Look for teacher - using method B
enteredName = "ninth";
System.out.println("B. Found " + enteredName + " : " + findTeacherB(teacherList, enteredName));
enteredName = "second";
System.out.println("B. Found " + enteredName + " : " + findTeacherB(teacherList, enteredName));
// Look for teacher - using method C
enteredName = "third";
System.out.println("C. Found " + enteredName + " : " + findTeacherC(teacherList, enteredName));
enteredName = "ninth";
System.out.println("C. Found " + enteredName + " : " + findTeacherC(teacherList, enteredName));
}
private static boolean findTeacherA(List<Teacher> teacherList, String enteredName) {
for (Teacher teacher : teacherList) {
if (teacher.getName().equals(enteredName)) {
// a match is found
return true;
}
}
return false;
}
private static boolean findTeacherB(List<Teacher> teacherList, String enteredName) {
return teacherList.stream()
.anyMatch(teacher -> teacher.getName().equals(enteredName));
}
private static boolean findTeacherC(List<Teacher> teacherList, String enteredName) {
Teacher enteredTeacher = new Teacher(enteredName);
return teacherList.contains(enteredTeacher);
}
}
輸出：
Teachers: [first, second, third]
A. Found ninth : false
A. Found first : true
B. Found ninth : false
B. Found second : true
C. Found third : true
C. Found ninth : false
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