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BAEL-6813: Creating a Magic Square in Java (eugenp#14572)
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‎core-java-modules/core-java-leetcode/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<artifactId>core-java-leetcode</artifactId>
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<name>core-java-leetcode</name>
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<packaging>jar</packaging>
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<parent>
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<groupId>com.baeldung</groupId>
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<artifactId>parent-modules</artifactId>
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<version>1.0.0-SNAPSHOT</version>
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<relativePath>../../pom.xml</relativePath>
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</parent>
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<dependencies>
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</dependencies>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<version>${maven-compiler-plugin.version}</version>
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<configuration>
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<source>${maven.compiler.source.version}</source>
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<target>${maven.compiler.target.version}</target>
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</configuration>
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</plugin>
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</plugins>
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</build>
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<properties>
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<maven.compiler.source.version>11</maven.compiler.source.version>
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<maven.compiler.target.version>11</maven.compiler.target.version>
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</properties>
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</project>

‎core-java-modules/core-java-leetcode/src/test/java/com/baeldung/leetcode/magicsquare/GenerationUnitTest.java‎

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package com.baeldung.leetcode.magicsquare;
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import org.junit.jupiter.api.Test;
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public class GenerationUnitTest {
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@Test
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public void testGenerate3x3() {
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MagicSquare magicSquare = new MagicSquare(3);
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System.out.println(magicSquare);
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magicSquare.validate();
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}
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@Test
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public void testGenerate9x9() {
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MagicSquare magicSquare = new MagicSquare(9);
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System.out.println(magicSquare);
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magicSquare.validate();
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}
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@Test
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public void testGenerate12x12() {
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MagicSquare magicSquare = new MagicSquare(12);
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System.out.println(magicSquare);
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magicSquare.validate();
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}
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@Test
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public void testGenerate10x10() {
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MagicSquare magicSquare = new MagicSquare(10);
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System.out.println(magicSquare);
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magicSquare.validate();
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}
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@Test
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public void testGenerate18x18() {
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MagicSquare magicSquare = new MagicSquare(18);
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System.out.println(magicSquare);
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magicSquare.validate();
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}
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}

‎core-java-modules/core-java-leetcode/src/test/java/com/baeldung/leetcode/magicsquare/MagicSquare.java‎

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package com.baeldung.leetcode.magicsquare;
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import org.junit.platform.commons.util.StringUtils;
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import java.util.stream.IntStream;
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public class MagicSquare {
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private int[][] cells;
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public MagicSquare(int n) {
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this.cells = new int[n][];
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for (int i = 0; i < n; ++i) {
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this.cells[i] = new int[n];
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}
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if (n % 2 == 1) {
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populateOdd();
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} else if (n % 4 == 0) {
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populateDoubleEven();
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} else if (n >= 6) {
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populateSingleEven();
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}
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}
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private void populateOdd() {
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int n = getN();
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populateOddArea(0, 0, n, 0);
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}
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private void populateOddArea(int xOffset, int yOffset, int n, int numberOffset) {
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int y = 0;
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int x = (n - 1) / 2;
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setCell(xOffset + x, yOffset + y, numberOffset + 1);
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for (int number = 2; number <= n * n; ++number) {
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int nextX = x + 1;
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if (nextX == n) {
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nextX = 0;
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}
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int nextY = y - 1;
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if (nextY == -1) {
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nextY = n - 1;
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}
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if (getCell(xOffset + nextX, yOffset + nextY) != 0) {
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nextX = x;
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nextY = y + 1;
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if (nextY == n) {
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nextY = 0;
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}
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}
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setCell(xOffset + nextX, yOffset + nextY, numberOffset + number);
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x = nextX;
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y = nextY;
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}
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}
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private void populateDoubleEven() {
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int n = getN();
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int number = 1;
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for (int y = 0; y < n; ++y) {
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for (int x = 0; x < n; ++x) {
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boolean highlighted = false;
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if ((y < n/4 || y >= 3*n/4) && (x >= n/4 && x < 3*n/4)) {
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highlighted = true;
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} else if ((x < n/4 || x >= 3*n/4) && (y >= n/4 && y < 3*n/4)) {
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highlighted = true;
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}
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if (highlighted) {
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setCell(x, y, (n * n) - number + 1);
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} else {
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setCell(x, y, number);
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}
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number += 1;
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}
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}
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}
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private void populateSingleEven() {
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int n = getN();
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int halfN = n/2;
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int swapSize = (int) n/4;
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populateOddArea(0, 0, halfN, 0);
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populateOddArea(halfN, halfN, halfN, halfN * halfN);
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populateOddArea(halfN, 0, halfN, (halfN * halfN) * 2);
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populateOddArea(0, halfN, halfN, (halfN * halfN) * 3);
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for (int x = 0; x < swapSize; ++x) {
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swapCells(x, 0, x, halfN);
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swapCells(x, halfN - 1, x, n - 1);
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for (int y = 1; y < halfN - 1; ++y) {
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swapCells(x + 1, y, x + 1, y + halfN);
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}
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}
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for (int x = 0; x < swapSize - 1; ++x) {
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for (int y = 0; y < halfN; ++y) {
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swapCells(n - x - 1, y, n - x - 1, y + halfN);
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}
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}
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}
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private void swapCells(int x1, int y1, int x2, int y2) {
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int cell1 = getCell(x1, y1);
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int cell2 = getCell(x2, y2);
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setCell(x1, y1, cell2);
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setCell(x2, y2, cell1);
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}
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public int getN() {
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return cells.length;
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}
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public int getCell(int x, int y) {
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return cells[x][y];
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}
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public void setCell(int x, int y, int value) {
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cells[x][y] = value;
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}
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public void validate() {
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int n = getN();
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int expectedValue = ((n * n * n) + n) / 2;
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// Diagonals
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if (IntStream.range(0, n).map(i -> getCell(i, i)).sum() != expectedValue) {
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throw new IllegalStateException("Leading diagonal is not the expected value");
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}
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if (IntStream.range(0, n).map(i -> getCell(i, n - i - 1)).sum() != expectedValue) {
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throw new IllegalStateException("Trailing diagonal is not the expected value");
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}
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// Rows
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IntStream.range(0, n).forEach(y -> {
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if (IntStream.range(0, n).map(x -> getCell(x, y)).sum() != expectedValue) {
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throw new IllegalStateException("Row is not the expected value");
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}
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});
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// Cols
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IntStream.range(0, n).forEach(x -> {
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if (IntStream.range(0, n).map(y -> getCell(x, y)).sum() != expectedValue) {
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throw new IllegalStateException("Column is not the expected value");
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}
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});
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}
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public String toString() {
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int n = getN();
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int largestNumberLength = Integer.toString(n * n).length();
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String formatString = " %0" + largestNumberLength + "d ";
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StringBuilder sb = new StringBuilder();
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for (int y = 0; y < n; ++y) {
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for (int x = 0; x < n; ++x) {
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int value = getCell(x, y);
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if (value == 0) {
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sb.append(" ");
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sb.append(".".repeat(largestNumberLength));
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sb.append(" ");
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} else {
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sb.append(String.format(formatString, value));
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}
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}
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sb.append("\n");
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}
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return sb.toString();
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}
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}

‎core-java-modules/core-java-leetcode/src/test/java/com/baeldung/leetcode/magicsquare/ValidationUnitTest.java‎

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package com.baeldung.leetcode.magicsquare;
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import org.junit.jupiter.api.Test;
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public class ValidationUnitTest {
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@Test
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public void testValidate3x3() {
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MagicSquare magicSquare = new MagicSquare(3);
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magicSquare.setCell(0, 0, 8);
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magicSquare.setCell(1, 0, 1);
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magicSquare.setCell(2, 0, 6);
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magicSquare.setCell(0, 1, 3);
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magicSquare.setCell(1, 1, 5);
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magicSquare.setCell(2, 1, 7);
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magicSquare.setCell(0, 2, 4);
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magicSquare.setCell(1, 2, 9);
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magicSquare.setCell(2, 2, 2);
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magicSquare.validate();
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}
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}

‎core-java-modules/pom.xml‎

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<module>core-java-lang-operators-2</module>
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<module>core-java-lang-syntax</module>
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<module>core-java-lang-syntax-2</module>
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<module>core-java-leetcode</module>
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<module>core-java-locale</module>
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<module>core-java-networking</module>
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<module>core-java-networking-2</module>

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