Java

 https://www.youtube.com/watch?v=X80nJ5T7YpE Spring Boot + JWT

https://www.youtube.com/watch?v=t4-416mg6iU  OAuth

/libs/some.jar

mvn install:install-file -Dfile=some.jar -DgroupId=asdf.com -DartifactId=artif -Dversion=1.9.9 -Dpackaging=jar -DgeneratePom=true

Spring Boot

Create new test: Ctrl +  Shift + t

Security:

 https://amigoscode.com/courses/728126/lectures/13124158

https://www.youtube.com/watch?v=KxqlJblhzfI

https://www.youtube.com/watch?v=b9O9NI-RJ3o

Dan Vega: 

https://www.youtube.com/playlist?list=PLZV0a2jwt22s5NCKOwSmHVagoDW8nflaC

ObjectMapper:

https://fasterxml.github.io/jackson-databind/javadoc/2.7/com/fasterxml/jackson/databind/ObjectMapper.html

https://www.baeldung.com/jackson-object-mapper-tutorial

https://link.springer.com/book/10.1007/978-1-4842-3676-5

Pro Spring Boot 2

An Authoritative Guide to Building Microservices, Web and Enterprise Applications, and Best Practices

@Entity

@PrePersist

void onCreate() {

this.setCreated(LocalDateTime.now());

this.setModified(LocalDateTime.now());

}

@PreUpdate

void onUpdate() {

this.setModified(LocalDateTime.now());

}

# H2-Console: http://localhost:8080/h2-console

# jdbc:h2:mem:testdb

spring.h2.console.enabled=true

<form id="logout" action="/logout" method="POST">

<input type="hidden" name="_csrf" value="{{_csrf.token}}" />

</form>

<script>

$(function(){

$('#logoutLink').click(function(){

$('#logout').submit();

});

});

</script>

JAVA DTO Pattern Tutorial 

https://www.youtube.com/watch?v=5yquJa2x3Ko&t=193s

RuntimeException:

@ResponseStatus(HttpStatus.NOT_FOUND)
public class TestRuntimeException extends RuntimeException{
    public TestRuntimeException(String id_not_found) {
    }
}

String to JSON: https://github.com/amigoscode/java-streams/blob/main/src/test/java/com/amigoscode/mockdata/MockData.java

public static List<Person> getPeople() throws IOException {

    InputStream inputStream = Resources.getResource("people.json").openStream();

    String json = IOUtils.toString(inputStream, StandardCharsets.UTF_8);

    Type listType = new TypeToken<ArrayList<Person>>() {

    }.getType();

    return new Gson().fromJson(json, listType);

}

spring-data-jpa-course: https://github.com/amigoscode/spring-data-jpa-course/blob/section-7/src/main/resources/application.properties

spring.datasource.url=jdbc:postgresql://localhost:5432/amigoscode

spring.datasource.username=

spring.datasource.password=

spring.jpa.hibernate.ddl-auto=create-drop

spring.jpa.show-sql=true

spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.PostgreSQLDialect

spring.jpa.properties.hibernate.format_sql=true

spring.h2.console.enabled=true

spring.datasource.url=jdbc:h2:mem:testdb;DB_CLOSE_DELAY=-1

spring.datasource.username=sa

spring.datasource.password=

spring.datasource.driver-class-name=org.h2.Driver

spring.jpa.hibernate.ddl-auto=create-drop

spring.jpa.show-sql=true

spring.jpa.properties.hibernate.format_sql=true

server.error.include-message=always

server.error.include-binding-errors=always

spring:
  h2.console.enabled: true
  datasource:
    url: jdbc:h2:mem:testdb;DB_CLOSE_DELAY=-1
    username: sa
    password:
    driver-class-name: org.h2.Driver
  jpa:
    hibernate.ddl-auto: create-drop
    show-sql: true
    defer-datasource-initialization: true
#    properties.hibernate.format_sql: true

postgresql tips: https://youtu.be/9SGDpanrc8U?t=2273

@Bean
	CommandLineRunner commandLineRunner() {
	return args -> {
	System.out.println("Command line runner hooray");
	};
	}

@Transient means the field is not for DB

Spring Data JPA https://www.youtube.com/watch?v=8SGI_XS5OPw

How To Handle Exceptions 

https://www.youtube.com/watch?v=PzK4ZXa2Tbc

https://www.youtube.com/watch?v=jFZ4lLLkT7M

??? complete course??? https://www.youtube.com/watch?v=8SGI_XS5OPw&list=PLwvrYc43l1MzeA2bBYQhCWr2gvWLs9A7S

fullstack https://www.youtube.com/watch?v=i-hoSg8iRG0&list=PLwvrYc43l1MzeA2bBYQhCWr2gvWLs9A7S&index=4

Spring Security Tutorial - [NEW] [2023] https://www.youtube.com/watch?v=b9O9NI-RJ3o

@Bean

CommandLineRunner commandLineRunner() {

    return args -> {

        System.out.println(Arrays.toString(args));

    };

}

Software Testing Tutorial - Learn Unit Testing and Integration Testing: https://www.youtube.com/watch?v=Geq60OVyBPg

Mockito: https://youtu.be/Geq60OVyBPg?t=2835

@ExtendWith(MockitoExtension.class)

ArgumentCaptor: https://youtu.be/Geq60OVyBPg?t=3506

given(repo.findById(anyInt()),willReturn(true)

Microservices Using Spring Boot and Spring Cloud

https://www.youtube.com/watch?v=p485kUNpPvE&list=PLwvrYc43l1Mwqpf9i-1B1gXfMeHOm6DeY

10 common mistakes:

Constructor Dependency Injection (not setter)

DefaultExceptionHandler https://youtu.be/CT8dbbe783s?t=558

Select properJava collection

 

https://github.com/encapsulin/coreJava/blob/main/src/speedCalc/MainCollections.java

-=start=-

///////////////////////////////

addFirst()class java.util.ArrayDeque1000000: 134 ms 

addFirst()class java.util.ArrayDeque2000000: 107 ms 

addFirst()class java.util.ArrayDeque3000000: 60 ms 

addFirst()class java.util.ArrayDeque4000000: 70 ms 

addFirst()class java.util.ArrayDeque5000000: 105 ms 

removeFirst()class java.util.ArrayDeque: 22 ms 

addFirst()class java.util.LinkedList1000000: 285 ms 

addFirst()class java.util.LinkedList2000000: 38 ms 

addFirst()class java.util.LinkedList3000000: 176 ms 

addFirst()class java.util.LinkedList4000000: 155 ms 

addFirst()class java.util.LinkedList5000000: 152 ms 

removeFirst()class java.util.LinkedList: 85 ms 

addFirst()class java.util.ArrayList50000: 194 ms 

addFirst()class java.util.ArrayList100000: 615 ms 

addFirst()class java.util.ArrayList150000: 1080 ms 

addFirst()class java.util.ArrayList200000: 1509 ms 

addFirst()class java.util.ArrayList250000: 1941 ms 

removeFirst()class java.util.ArrayList: 5289 ms 

///////////////////////////////

addLast()class java.util.ArrayList1000000: 32 ms 

addLast()class java.util.ArrayList2000000: 78 ms 

addLast()class java.util.ArrayList3000000: 25 ms 

addLast()class java.util.ArrayList4000000: 18 ms 

addLast()class java.util.ArrayList5000000: 37 ms 

removeLast()class java.util.ArrayList: 27 ms 

addLast()class java.util.ArrayDeque1000000: 50 ms 

addLast()class java.util.ArrayDeque2000000: 18 ms 

addLast()class java.util.ArrayDeque3000000: 29 ms 

addLast()class java.util.ArrayDeque4000000: 18 ms 

addLast()class java.util.ArrayDeque5000000: 18 ms 

removeLast()class java.util.ArrayDeque: 55 ms 

addLast()class java.util.LinkedList1000000: 157 ms 

addLast()class java.util.LinkedList2000000: 211 ms 

addLast()class java.util.LinkedList3000000: 210 ms 

addLast()class java.util.LinkedList4000000: 15 ms 

addLast()class java.util.LinkedList5000000: 214 ms 

removeLast()class java.util.LinkedList: 86 ms 

///////////////////////////////

addMiddle()class java.util.ArrayList50000: 86 ms 

removeMiddle()class java.util.ArrayList: 89 ms 

addMiddle()class java.util.LinkedList50000: 1480 ms 

removeMiddle()class java.util.LinkedList: 1479 ms 

addMiddle()class java.util.ArrayDeque50000: 16636 ms 

-=stop=-

foxminded

https://youtu.be/IFL7qnRR6YE?t=2070

https://youtu.be/IFL7qnRR6YE?t=5895

Java Map

Map map = new HashMap<>(); 

IntStream.range(0,4).forEach(i->map.put("str"+i,i)); 

System.out.println(map);

 ///////////////////////////////////////////

   

        List<Map.Entry<String, Integer>> list = map.entrySet().stream()

                .sorted(Map.Entry.comparingByValue(Comparator.reverseOrder()))

                .sorted((a,b)->b.getValue()-a.getValue())

                .limit(3).collect(Collectors.toList());

        System.out.printf("\nList:%s:%d", list.get(0).getKey(), list.get(0).getValue());

        list.forEach(entry -> System.out.printf("\n%s:%d", entry.getKey(), entry.getValue()));

        Optional<Map.Entry<String, Integer>> opt = map.entrySet().stream()

                .sorted(Map.Entry.comparingByValue(Comparator.reverseOrder()))

                .limit(3).findFirst();

        System.out.printf("\nOpt:%s:%d", opt.get().getKey(), opt.get().getValue());

Map<String, Integer> map2 = map.entrySet().stream()

                .sorted((a,b)->b.getValue()-a.getValue())

                .limit(1).collect(Collectors.toMap(m->m.getKey(),m->m.getValue()));

        System.out.println("map2:" + map2);

/////////////////////////////////////////////////////////////////////////////////////////////////////////////

map.forEach((k, v) -> System.out.println((k + ":" + v)));

map.entrySet().stream()
        .forEach(e -> System.out.println(e.getKey() + ":" + e.getValue()));

for (Map.Entry<String, Integer> entry : map.entrySet()) { System.out.println(entry.getKey() + ":" + entry.getValue()); }

for (String key : map.keySet()) { System.out.println(key + ":" + map.get(key)); }

for (Integer value : map.values()) { System.out.println(value); }

Java ArrayDeque

ArrayDeque<Integer> q = new ArrayDeque<>();

IntStream.range(0, 5).forEach((i) -> {q.addFirst(i);});
System.out.println(q);

IntStream.range(0, 5).forEach((i) -> {
            System.out.printf("%d, ", q.pollFirst());
        }        );

System.out.println(q);

        ArrayDeque<Integer> q = new ArrayDeque<>();

        IntStream.range(0, 5).forEach((i) -> { q.addFirst(i);  });

        System.out.println(q);

//[4, 3, 2, 1, 0]

        IntStream.range(0, 5).forEach((i) ->{System.out.printf("%d,",q.pollFirst());});

//4, 3, 2, 1, 0, 

        System.out.println(q); //[]

        //q.clear();

 ###################################

Java Collections

 https://www.programcreek.com/2014/04/check-if-array-contains-a-value-java/

1. Four Different Ways to Check If an Array Contains a Value

1) Using List:

public static boolean useList(String[] arr, String targetValue) { return Arrays.asList(arr).contains(targetValue); }

2) Using Set:

public static boolean useSet(String[] arr, String targetValue) { Set<String> set = new HashSet<String>(Arrays.asList(arr)); return set.contains(targetValue); }

3) Using a simple loop:

public static boolean useLoop(String[] arr, String targetValue) { for(String s: arr){ if(s.equals(targetValue)) return true; } return false; }

4) Using Arrays.binarySearch():
binarySearch() can ONLY be used on sorted arrays. If the array is sorted, you can use the following code to search the target element:

public static boolean useArraysBinarySearch(String[] arr, String targetValue) { int a = Arrays.binarySearch(arr, targetValue); if(a > 0) return true; else return false; }

Comparator<Arrow> cmp = Comparator
        .comparing(Arrow::getWeight)
        .thenComparing(Arrow::getCount, Comparator.reverseOrder())
        .thenComparing((a, b) -> Character.compare(a.ch, b.ch));

listChar.sort(cmp);

 
List<Employee> sortedEmployees = employees.stream()
                .sorted(cmp).collect(Collectors.toList());

////////////////////////////////////////////////////////////////////////////////////////////////////////// 

 Collections.sort(scores, new Comparator<Score>() {

        public int compare(Score o1, Score o2) {
            return o2.getScores().get(0).compareTo(o1.getScores().get(0));
        }
    });

Collections.sort(scores, (s1, s2) -> { return s1 - s2; });

Collections.binarySearch(cats, key);

String s = list.stream().map(Objects::toString)
.sorted(Comparator.reverseOrder()).collect(Collectors.joining(""));

int[] arr = {1,2,3};

var list = Arrays.stream(arr).boxed().toList();

list.subArray(int begin, int end)

Class StringBuilder

Modifier and Type	Method and Description
StringBuilder	append(boolean b)
StringBuilder	append(char c)
StringBuilder	append(char[] str)
StringBuilder	append(char[] str, int offset, int len)
StringBuilder	append(CharSequence s)
StringBuilder	append(CharSequence s, int start, int end)
StringBuilder	append(double d)
StringBuilder	append(float f)
StringBuilder	append(int i)
StringBuilder	append(long lng)
StringBuilder	append(Object obj)
StringBuilder	append(String str)
StringBuilder	append(StringBuffer sb)
StringBuilder	appendCodePoint(int codePoint)
int	capacity()
char	charAt(int index)
int	codePointAt(int index)
int	codePointBefore(int index)
int	codePointCount(int beginIndex, int endIndex)
StringBuilder	delete(int start, int end)
StringBuilder	deleteCharAt(int index)
void	ensureCapacity(int minimumCapacity)
void	getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
int	indexOf(String str)
int	indexOf(String str, int fromIndex)
StringBuilder	insert(int offset, boolean b)
StringBuilder	insert(int offset, char c)
StringBuilder	insert(int offset, char[] str)
StringBuilder	insert(int index, char[] str, int offset, int len)
StringBuilder	insert(int dstOffset, CharSequence s)
StringBuilder	insert(int dstOffset, CharSequence s, int start, int end)
StringBuilder	insert(int offset, double d)
StringBuilder	insert(int offset, float f)
StringBuilder	insert(int offset, int i)
StringBuilder	insert(int offset, long l)
StringBuilder	insert(int offset, Object obj)
StringBuilder	insert(int offset, String str)
int	lastIndexOf(String str)
int	lastIndexOf(String str, int fromIndex)
int	length()
int	offsetByCodePoints(int index, int codePointOffset)
StringBuilder	replace(int start, int end, String str)
StringBuilder	reverse()
void	setCharAt(int index, char ch)
void	setLength(int newLength)
CharSequence	subSequence(int start, int end)
String	substring(int start)
String	substring(int start, int end)
String	toString()
void	trimToSize()

Class String

Modifier and Type	Method and Description
char	charAt(int index)
int	codePointAt(int index)
int	codePointBefore(int index)
int	codePointCount(int beginIndex, int endIndex)
int	compareTo(String anotherString)
int	compareToIgnoreCase(String str)
String	concat(String str)
boolean	contains(CharSequence s)
boolean	contentEquals(CharSequence cs)
boolean	contentEquals(StringBuffer sb)
static String	copyValueOf(char[] data) Equivalent to valueOf(char[]).
static String	copyValueOf(char[] data, int offset, int count) Equivalent to valueOf(char[], int, int).
boolean	endsWith(String suffix)
boolean	equals(Object anObject)
boolean	equalsIgnoreCase(String anotherString)
static String	format(Locale l, String format, Object... args) Returns a formatted string using the specified locale, format string, and arguments.
static String	format(String format, Object... args) Returns a formatted string using the specified format string and arguments.
byte[]	getBytes()
byte[]	getBytes(Charset charset)
void	getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin) Deprecated.  This method does not properly convert characters into bytes. As of JDK 1.1, the preferred way to do this is via the getBytes() method, which uses the platform's default charset.
byte[]	getBytes(String charsetName)
void	getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
int	hashCode()
int	indexOf(int ch)
int	indexOf(int ch, int fromIndex)
int	indexOf(String str)
int	indexOf(String str, int fromIndex)
String	intern()
boolean	isEmpty()
static String	join(CharSequence delimiter, CharSequence... elements)
static String	join(CharSequence delimiter, Iterable<? extends CharSequence> elements)
int	lastIndexOf(int ch)
int	lastIndexOf(int ch, int fromIndex)
int	lastIndexOf(String str)
int	lastIndexOf(String str, int fromIndex)
int	length()
boolean	matches(String regex)
int	offsetByCodePoints(int index, int codePointOffset)
boolean	regionMatches(boolean ignoreCase, int toffset, String other, int ooffset, int len)
boolean	regionMatches(int toffset, String other, int ooffset, int len)
String	replace(char oldChar, char newChar)
String	replace(CharSequence target, CharSequence replacement)
String	replaceAll(String regex, String replacement)
String	replaceFirst(String regex, String replacement)
String[]	split(String regex)
String[]	split(String regex, int limit)
boolean	startsWith(String prefix)
boolean	startsWith(String prefix, int toffset)
CharSequence	subSequence(int beginIndex, int endIndex)
String	substring(int beginIndex)
String	substring(int beginIndex, int endIndex)
char[]	toCharArray()
String	toLowerCase()
String	toLowerCase(Locale locale)
String	toString()
String	toUpperCase()
String	toUpperCase(Locale locale)
String	trim()
static String	valueOf(boolean b) Returns the string representation of the boolean argument.
static String	valueOf(char c) Returns the string representation of the char argument.
static String	valueOf(char[] data) Returns the string representation of the char array argument.
static String	valueOf(char[] data, int offset, int count) Returns the string representation of a specific subarray of the char array argument.
static String	valueOf(double d) Returns the string representation of the double argument.
static String	valueOf(float f) Returns the string representation of the float argument.
static String	valueOf(int i) Returns the string representation of the int argument.
static String	valueOf(long l) Returns the string representation of the long argument.
static String	valueOf(Object obj) Returns the string representation of the Object argument.