java-stream

问题 This question already has answers here : Java 8 Lambda function that throws exception? (26 answers) Closed 4 years ago . I have the following code snippet. package web_xtra_klasa.utils; import java.util.Arrays; import java.util.Properties; import java.util.function.Function; import javax.mail.Message; import javax.mail.MessagingException; import javax.mail.Session; import javax.mail.Transport; import javax.mail.internet.InternetAddress; import javax.mail.internet.MimeMessage; public class

问题 I wanted to convert list to Map as below. Here is the example. I have student list something like below code snippet. Get a Hasmap out of it with Key as Integer which is Age and value as List. From the below input feed, My response should be something like below. How do I achieve this ? Map[[10, {1}], [20, {2,3,4}], [30,{5}]. [40,{6}]]; private static List<Person> getPersonTestData() { List<Person> personList = new ArrayList<>(); personList.add(Person.of(1, "First1", "Last1", 10)); personList

问题 I have a HashMap<Integer, Integer> , There can be duplicate values for the unique keys. Is there a way to convert the HashMap to a Set<Integer> which contains unique Integers of both the keys and values. This can definitely be done in two loops by iterating over the keySet() and .values(). I'm would like to know whether this is possible in java 8 streams. 回答1: You can use the stream function to combine both the values and the keys: Map<Integer, Integer> map = ... Set<Integer> total = Stream

问题 This question already has answers here : Java 8 Streams peek api (4 answers) How to use Streams api peek() function and make it work? (2 answers) Closed 2 years ago . I've got 2 statements, I expected that they should "print" same result: Arrays.stream("abc".split("")).forEach(System.out::println);//first Arrays.stream("abc".split("")).peek(new Consumer<String>() {//second @Override public void accept(String s) { System.out.println(s);//breakpoint } }); In fact, the first statement will print

问题 This question already has answers here : Java 8 Streams peek api (4 answers) How to use Streams api peek() function and make it work? (2 answers) Closed 2 years ago . I've got 2 statements, I expected that they should "print" same result: Arrays.stream("abc".split("")).forEach(System.out::println);//first Arrays.stream("abc".split("")).peek(new Consumer<String>() {//second @Override public void accept(String s) { System.out.println(s);//breakpoint } }); In fact, the first statement will print

问题 We have a Student class as follows: class Student { private int marks; private String studentName; public int getMarks() { return marks; } public void setMarks(int marks) { this.marks = marks; } public String getStudentName() { return studentName; } public void setStudentName(String studentName) { this.studentName = studentName; } public Student(String studentName, int marks) { this.marks = marks; this.studentName = studentName; } } We have a LIST of Students as follows : List<Student>

问题 We have a Student class as follows: class Student { private int marks; private String studentName; public int getMarks() { return marks; } public void setMarks(int marks) { this.marks = marks; } public String getStudentName() { return studentName; } public void setStudentName(String studentName) { this.studentName = studentName; } public Student(String studentName, int marks) { this.marks = marks; this.studentName = studentName; } } We have a LIST of Students as follows : List<Student>

问题 We have a Student class as follows: class Student { private int marks; private String studentName; public int getMarks() { return marks; } public void setMarks(int marks) { this.marks = marks; } public String getStudentName() { return studentName; } public void setStudentName(String studentName) { this.studentName = studentName; } public Student(String studentName, int marks) { this.marks = marks; this.studentName = studentName; } } We have a LIST of Students as follows : List<Student>

问题 I am using the Stream API introduced in Java 8 to run a method for each string in a list. public boolean initFile() throws IOException { if (this.outFile.exists()) { this.outFile.delete(); } return this.outFile.createNewFile(); } public void writeStringToFile(String str, boolean addNewLine) throws IOException { if (this.mode != FileMode.READ) { if (this.initFile()) { FileWriter fileWriter; if (this.mode == FileMode.APPEND) fileWriter = new FileWriter(outFile.getAbsolutePath(), true); else

问题 I am using the Stream API introduced in Java 8 to run a method for each string in a list. public boolean initFile() throws IOException { if (this.outFile.exists()) { this.outFile.delete(); } return this.outFile.createNewFile(); } public void writeStringToFile(String str, boolean addNewLine) throws IOException { if (this.mode != FileMode.READ) { if (this.initFile()) { FileWriter fileWriter; if (this.mode == FileMode.APPEND) fileWriter = new FileWriter(outFile.getAbsolutePath(), true); else