如何便捷地将两个数组合到一起

Author: giantray

README.md

@@ -24,6 +24,7 @@ stackoverflow-Java-top-qa
 * [如何分割（split）string字符串](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-split-a-string-in-java.md)
 * [在java中如何对比（compare）string](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-do-i-compare-strings-in-java.md)
 * [`Map<Key,Value>`基于Value值排序](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-sort-a-mapkey-value-on-the-values-in-java.md)
+* [如何便捷地将两个数组合到一起](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-concatenate-two-arrays-in-java.md)
 
 > 编程技巧
 
@@ -75,7 +76,6 @@ stackoverflow-Java-top-qa
 - [Comparing Java enum members: == or equals()?](http://stackoverflow.com/questions/1750435/comparing-java-enum-members-or-equals)
 - [Failed to load the JNI shared Library (JDK)](http://stackoverflow.com/questions/7352493/failed-to-load-the-jni-shared-library-jdk)
 - [Does Java support default parameter values?](http://stackoverflow.com/questions/997482/does-java-support-default-parameter-values)
-- [How to concatenate two arrays in Java?](http://stackoverflow.com/questions/80476/how-to-concatenate-two-arrays-in-java)
 - [What's the simplest way to print a Java array?](http://stackoverflow.com/questions/409784/whats-the-simplest-way-to-print-a-java-array)
 - [Why can't I switch on a String?](http://stackoverflow.com/questions/338206/why-cant-i-switch-on-a-string)
 - [How to create a Java String from the contents of a file?](http://stackoverflow.com/questions/326390/how-to-create-a-java-string-from-the-contents-of-a-file)

contents/how-to-concatenate-two-arrays-in-java.md

@@ -0,0 +1,40 @@
+##如何便捷地将两个数组合到一起
+
+###一行代码搞定
+Apache Commons Lang library [`ArrayUtils.addAll(T[], T...)`](http://commons.apache.org/proper/commons-lang/javadocs/api-3.1/org/apache/commons/lang3/ArrayUtils.html#addAll%28T%5B%5D,%20T...%29)就是专门干这事的
+
+代码：
+```java
+String[] both = ArrayUtils.addAll(first, second);
+```
+
+###不借助依赖包
+
+####非泛型
+把下面的`Foo`替换成你自己的类名
+```java
+public Foo[] concat(Foo[] a, Foo[] b) {
+   int aLen = a.length;
+   int bLen = b.length;
+   Foo[] c= new Foo[aLen+bLen];
+   System.arraycopy(a, 0, c, 0, aLen);
+   System.arraycopy(b, 0, c, aLen, bLen);
+   return c;
+}
+```
+
+####泛型
+```java
+public <T> T[] concatenate (T[] a, T[] b) {
+    int aLen = a.length;
+    int bLen = b.length;
+
+    @SuppressWarnings("unchecked")
+    T[] c = (T[]) Array.newInstance(a.getClass().getComponentType(), aLen+bLen);
+    System.arraycopy(a, 0, c, 0, aLen);
+    System.arraycopy(b, 0, c, aLen, bLen);
+
+    return c;
+}
+```
+注意，泛型的方案不适用于基本数据类型（int，boolean……)