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update basics (#105)
* static example * date example * for in * add range function * return example * constructor example * update this keyword * Formatted with Google Java Formatter Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
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‎src/main/java/com/examplehub/basics/CalendarExample.java‎

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package com.examplehub.basics;
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import java.util.Calendar;
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public class CalendarExample {
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public static void main(String[] args) {
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Calendar calendar = Calendar.getInstance();
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System.out.println(calendar);
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}
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}

‎src/main/java/com/examplehub/basics/ConstructorExample.java‎

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package com.examplehub.basics;
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public class ConstructorExample {
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public static void main(String[] args) {
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ConstructorTest test = new ConstructorTest();
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System.out.println(test); /* ConstructorTest{username='admin', password='112233'} */
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test = new ConstructorTest("root", "root");
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System.out.println(test); /* ConstructorTest{username='root', password='root'} */
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}
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}
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class ConstructorTest {
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public String username;
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public String password;
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public ConstructorTest() {
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this("admin", "112233");
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}
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public ConstructorTest(String username, String password) {
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this.username = username;
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this.password = password;
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}
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@Override
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public String toString() {
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return "ConstructorTest{"
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+ "username='"
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+ username
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+ '\''
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+ ", password='"
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+ password
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+ '\''
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+ '}';
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}
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}

‎src/main/java/com/examplehub/basics/DateExample.java‎

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package com.examplehub.basics;
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import java.util.Date;
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public class DateExample {
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public static void main(String[] args) {
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System.out.println(new Date());
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}
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}

‎src/main/java/com/examplehub/basics/ForInExample.java‎

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package com.examplehub.basics;
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import java.util.ArrayList;
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import java.util.List;
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public class ForInExample {
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public static void main(String[] args) {
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int[] numbers = {5, 55, 555, 5555, 55555};
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/*
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* 5
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* 55
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* 555
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* 5555
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* 55555
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*/
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for (int number : numbers) {
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System.out.println(number);
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}
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/*
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* E
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* H
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*/
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for (char ch : "ExampleHub".toCharArray()) {
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if (Character.isUpperCase(ch)) {
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System.out.println(ch);
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}
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}
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/*
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* Java
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* Python
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* C
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*/
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List<String> books =
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new ArrayList<String>() {
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{
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add("Java");
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add("Python");
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add("C");
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}
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};
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for (String book : books) {
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System.out.println(book);
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}
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}
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}

‎src/main/java/com/examplehub/basics/ReturnExample.java‎

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package com.examplehub.basics;
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public class ReturnExample {
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public static void main(String[] args) {
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System.out.println(test(15, 10)); /* 1 */
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System.out.println(test(10, 15)); /* -1 */
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System.out.println(test(10, 10)); /* 0 */
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}
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private static int test(int test, int target) {
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if (test > target) {
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return 1;
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}
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if (test < target) {
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return -1;
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}
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return 0;
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}
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}

‎src/main/java/com/examplehub/basics/StaticExample.java‎

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package com.examplehub.basics;
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public class StaticExample {
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public static void main(String[] args) {
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StaticTest staticTest = new StaticTest();
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StaticTest.increment();
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System.out.println(StaticTest.count); /* 1 */
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staticTest.method(); /* normal method */
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System.out.println(StaticTest.count); /* 2 */
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}
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}
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class StaticTest {
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public static int count = 0;
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public static void increment() {
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count++;
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}
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public void method() {
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increment();
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System.out.println("normal method");
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}
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}

‎src/main/java/com/examplehub/basics/ThisKeywordExample.java‎

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rectangle = new Rectangle(1, 1, 3, 4);
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System.out.println(rectangle); /* Rectangle{x=1, y=1, width=3, height=4} */
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Counter counter = new Counter();
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System.out.println(counter.increment().increment().increment().getCount()); /* 3 */
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}
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}
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return "Rectangle{" + "x=" + x + ", y=" + y + ", width=" + width + ", height=" + height + '}';
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}
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}
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class Counter {
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private int count = 0;
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public Counter increment() {
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count++;
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return this;
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}
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public int getCount() {
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return count;
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}
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}

‎src/main/java/com/examplehub/maths/Range.java‎

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package com.examplehub.maths;
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import java.util.ArrayList;
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import java.util.List;
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public class Range {
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public static int[] range(int n) {
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List<Integer> numbers = new ArrayList<>();
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for (int i = 0; i < n; ++i) {
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numbers.add(i);
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}
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return numbers.stream().mapToInt(i -> i).toArray();
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}
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public static int[] range(int start, int end) {
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List<Integer> numbers = new ArrayList<>();
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for (int i = start; i < end; ++i) {
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numbers.add(i);
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}
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return numbers.stream().mapToInt(i -> i).toArray();
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}
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public static int[] range(int start, int end, int step) {
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List<Integer> numbers = new ArrayList<>();
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for (int i = start; i < end; i += step) {
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numbers.add(i);
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}
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return numbers.stream().mapToInt(i -> i).toArray();
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}
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}

‎src/test/java/com/examplehub/maths/RangeTest.java‎

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package com.examplehub.maths;
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import static org.junit.jupiter.api.Assertions.*;
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import java.util.Arrays;
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import org.junit.jupiter.api.Test;
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class RangeTest {
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@Test
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void testRange() {
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assertTrue(Arrays.equals(new int[] {0, 1, 2, 3, 4}, Range.range(5)));
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assertTrue(Arrays.equals(new int[] {10, 11, 12, 13, 14, 15}, Range.range(10, 16)));
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assertTrue(Arrays.equals(new int[] {1, 3, 5, 7, 9}, Range.range(1, 10, 2)));
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}
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}

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