add java

Author: DaviRain-Su

.DS_Store

@@ -1,4 +1,5 @@
-/target
+target
 node_modules
 lib
-*.bs.js
+*.bs.js
+.DS_Store

.gitignore

@@ -0,0 +1,19 @@
+# 算法
+
+## chapter1: basic
+
+算法的定义：一种有限、确定、有效的并适合用计算机程序来实现的解决问题的方法。
+
+算法是计算机科学的基础，是这个领域的核心。算法是一种解决问题的方法，是一种思维活动，是一种设计和分析的技术。
+
+欧几里得算法
+
+自然语言描述： 计算两个非负整数p和q的最大公约数：若q是0，则最大公约数为p。否则，将p除以q得到余数r，p和q的最大公约数即为q和r的最大公约数。
+
+```java
+public static int gcd(int p, int q) {
+    if (q == 0) return p;
+    int r = p % q;
+    return gcd(q, r);
+}
+```

java/README.md

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+<?xml version="1.0" encoding="UTF-8"?>
+
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>com.mycompany.app</groupId>
+  <artifactId>java</artifactId>
+  <version>1.0-SNAPSHOT</version>
+
+  <name>java</name>
+  <!-- FIXME change it to the project's website -->
+  <url>http://www.example.com</url>
+
+  <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    <maven.compiler.source>1.7</maven.compiler.source>
+    <maven.compiler.target>1.7</maven.compiler.target>
+    <maven.compiler.release>11</maven.compiler.release>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>4.11</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
+      <plugins>
+        <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
+        <plugin>
+          <artifactId>maven-clean-plugin</artifactId>
+          <version>3.1.0</version>
+        </plugin>
+        <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
+        <plugin>
+          <artifactId>maven-resources-plugin</artifactId>
+          <version>3.0.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-compiler-plugin</artifactId>
+          <version>3.8.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-surefire-plugin</artifactId>
+          <version>2.22.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-jar-plugin</artifactId>
+          <version>3.0.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-install-plugin</artifactId>
+          <version>2.5.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-deploy-plugin</artifactId>
+          <version>2.8.2</version>
+        </plugin>
+        <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
+        <plugin>
+          <artifactId>maven-site-plugin</artifactId>
+          <version>3.7.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-project-info-reports-plugin</artifactId>
+          <version>3.0.0</version>
+        </plugin>
+      </plugins>
+    </pluginManagement>
+  </build>
+</project>

java/pom.xml

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+package com.mycompany.app;
+
+import com.mycompany.binarysearch.BinarySearch;
+
+/**
+ * Hello world!
+ *
+ */
+public class App {
+
+    public static void main(String[] args) {
+        System.out.println("Hello Davirain!");
+        // test gcd
+        System.out.println(gcd(10, 5));
+        // test rank
+        int[] a = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
+        System.out.println(BinarySearch.rank(5, a));
+    }
+
+    /// gcd algorithm
+    public static int gcd(int p, int q) {
+        if (q == 0) {
+            return p;
+        } else {
+            return gcd(q, p % q);
+        }
+    }
+}

java/src/main/java/com/mycompany/app/App.java

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+package com.mycompany.binarysearch;
+
+import java.util.Arrays;
+
+/**
+ * Hello world!
+ *
+ */
+public class BinarySearch {
+
+    /// gcd algorithm
+    public static int gcd(int p, int q) {
+        if (q == 0) {
+            return p;
+        } else {
+            return gcd(q, p % q);
+        }
+    }
+
+    public static int rank(int key, int[] a) {
+        int lo = 0;
+        int hi = a.length - 1;
+        while (lo <= hi) {
+            // Key is in a[lo..hi] or not present.
+            int mid = lo + (hi - lo) / 2;
+            if (key < a[mid]) {
+                hi = mid - 1;
+            } else if (key > a[mid]) {
+                lo = mid + 1;
+            } else {
+                return mid;
+            }
+        }
+        return -1;
+    }
+}

java/src/main/java/com/mycompany/binarysearch/BinarySearch.java

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+package com.mycompany.app;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+/**
+ * Unit test for simple App.
+ */
+public class AppTest 
+{
+    /**
+     * Rigorous Test :-)
+     */
+    @Test
+    public void shouldAnswerWithTrue()
+    {
+        assertTrue( true );
+    }
+}