First commit

.gitignore

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+.gradle
+build/
+!gradle/wrapper/gradle-wrapper.jar
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### IntelliJ IDEA ###
+.idea/modules.xml
+.idea/jarRepositories.xml
+.idea/compiler.xml
+.idea/libraries/
+*.iws
+*.iml
+*.ipr
+out/
+!**/src/main/**/out/
+!**/src/test/**/out/
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+bin/
+!**/src/main/**/bin/
+!**/src/test/**/bin/
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store

.idea/.gitignore

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+# Default ignored files
+/shelf/
+/workspace.xml

.idea/artifacts/Lab1_jar.xml

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+<component name="ArtifactManager">
+  <artifact type="jar" name="Lab1:jar">
+    <output-path>$PROJECT_DIR$/out/artifacts/Lab1_jar</output-path>
+    <root id="archive" name="Lab1.jar">
+      <element id="module-output" name="Lab1" />
+    </root>
+  </artifact>
+</component>

.idea/discord.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="DiscordProjectSettings">
+    <option name="show" value="ASK" />
+    <option name="description" value="" />
+  </component>
+</project>

.idea/misc.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" default="true" project-jdk-name="1.8" project-jdk-type="JavaSDK">
+    <output url="file://$PROJECT_DIR$/out" />
+  </component>
+</project>

src/META-INF/MANIFEST.MF

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+Manifest-Version: 1.0
+Main-Class: Main
+

src/Main.java

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+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+
+public class Main {
+
+    public static void main(String[] args) {
+        System.out.println("Enter the quadratic equations coefficients (e.g. for x^2 + 2x + 0.9 = 0 enter 1 2 0.9");
+        while (true) {
+            BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
+            String input;
+            try {
+                input = reader.readLine();
+            } catch (IOException e) {
+                System.err.println("Failed to read user's input");
+                e.printStackTrace();
+                continue;
+            }
+            double[] coefficients = inputToDoubleArray(input);
+            if (coefficients == null) continue;
+            double[] solutions = solveEquation(coefficients);
+            switch (solutions.length) {
+                case 0:
+                    System.out.println("No real solutions");
+                    break;
+                case 1:
+                    System.out.printf("One real solution: x1 = %.3f\n", solutions[0]);
+                    break;
+                case 2:
+                    System.out.printf("Two real solutions: x1 = %.3f\tx2 = %.3f\n", solutions[0], solutions[1]);
+                    break;
+            }
+        }
+    }
+
+    private static double[] inputToDoubleArray(String input) {
+        String[] arr = input.trim().split(" ");
+        double[] coefficients = new double[3];
+        if (arr.length != 3) {
+            System.out.println("There must be only 3 arguments separated by a white space (e.g. 1 2 3)");
+            return null;
+        }
+
+        for (int i = 0; i < arr.length; i++) {
+            try {
+                double coefficient = Double.parseDouble(arr[i]);
+                coefficients[i] = coefficient;
+            } catch (NumberFormatException e) {
+                System.out.println("Your input should contain only numbers (if it's a float - use a dot instead of a comma e.g. 1.2)");
+                return null;
+            }
+        }
+        return coefficients;
+    }
+
+    private static double[] solveEquation(double... coefficients) {
+        double a = coefficients[0], b = coefficients[1], c = coefficients[2];
+        double d = b * b - 4 * a * c;
+        if (d < 0) return new double[]{};
+        double sqrtD = Math.sqrt(d);
+        double x1 = (-b + sqrtD) / (2 * a), x2 = (-b - sqrtD) / (2 * a);
+        if (d == 0) return new double[]{x1};
+        return new double[]{x1, x2};
+    }
+
+}