[add] add some examples in java-base module.

brianway · brianway · commit 0616b6e07441 · 2016-11-10T16:32:04.000+08:00
diff --git a/java-base/src/main/java/com/brianway/learning/java/base/Binary.java b/java-base/src/main/java/com/brianway/learning/java/base/Binary.java
@@ -0,0 +1,14 @@
+package com.brianway.learning.java.base;
+
+/**
+ * Created by brian on 16/11/10.
+ *
+ * TODO 补码/反码相关知识
+ */
+public class Binary {
+    public static void main(String[] args) {
+        int i = 5;
+        int j = 10;
+        System.out.println(i + ~j);
+    }
+}
diff --git a/java-base/src/main/java/com/brianway/learning/java/base/constructor/FatherClass.java b/java-base/src/main/java/com/brianway/learning/java/base/constructor/FatherClass.java
@@ -4,14 +4,19 @@
  * Created by Brian on 2016/4/14.
  */
 public class FatherClass {
+    protected static int count = 10;
     private String name;
 
+    static {
+        System.out.println("父类的静态属性count初始化:" + count);
+    }
+
     public FatherClass() {
         System.out.println("执行了父类的无参构造方法");
     }
 
     public FatherClass(String name) {
         this.name = name;
-        System.out.println("执行了父类的构造方法FatherClass(String name)");
+        System.out.println("执行了父类的构造方法FatherClass(String name) " + name);
     }
 }
diff --git a/java-base/src/main/java/com/brianway/learning/java/base/constructor/SonClass.java b/java-base/src/main/java/com/brianway/learning/java/base/constructor/SonClass.java
@@ -2,16 +2,22 @@
 
 /**
  * Created by Brian on 2016/4/14.
- */
-
-/**
+ *
  * 构造方法调用问题
  * 子类构造方法会首先默认调用父类的无参构造方法，无论是否显式写了super();
  */
 public class SonClass extends FatherClass {
+
+    private static int countSon;
+
+    static {
+        System.out.println("子类可以访问父类的静态属性count " + count);
+        System.out.println("子类的静态属性countSon初始化:" + countSon);
+    }
+
     public SonClass(String name) {
         //super(name);
-        System.out.println("执行了子类的构造方法SonClass(String name)");
+        System.out.println("执行了子类的构造方法SonClass(String name) " + name);
     }
 
     public SonClass() {
@@ -26,8 +32,11 @@ public static void main(String[] args) {
 }
 
 /*
+父类的静态属性count初始化:10
+子类可以访问父类的静态属性count 10
+子类的静态属性countSon初始化:0
 执行了父类的无参构造方法
-执行了子类的构造方法SonClass(String name)
+执行了子类的构造方法SonClass(String name) aaa
 执行了父类的无参构造方法
 执行了子类的无参构造方法
  */
diff --git a/java-base/src/main/java/com/brianway/learning/java/base/datatype/Boxing.java b/java-base/src/main/java/com/brianway/learning/java/base/datatype/Boxing.java
@@ -1,13 +1,11 @@
-package com.brianway.learning.java.base;
+package com.brianway.learning.java.base.datatype;
 
 /**
  * Created by Brian on 2016/4/14.
- */
-
-/**
- * TODO
- * 待理解。
- * 应该是考装箱和拆箱
+ *
+ * TODO 有些细节待理解
+ *
+ * 主要是考装箱和拆箱
  */
 public class Boxing {
     public static void main(String[] args) {
@@ -24,16 +22,19 @@ public static void main(String[] args) {
         System.out.println(c.equals(a + b));
         System.out.println(g == (a + b));
         System.out.println(g.equals(a + b));
+        System.out.println(new Integer(2) == new Integer(2));
 
     }
 }
 
 /*
-输出：
-true
-false
-true
+输出：               原因:
+true                自动装箱,缓存
+false               自动装箱,未缓存
 true
+true                调用 equals(),比较的是值,而不是对象地址
 true
 false
+false               比较的是对象地址
+
  */
diff --git a/java-base/src/main/java/com/brianway/learning/java/base/datatype/IntegerChanger.java b/java-base/src/main/java/com/brianway/learning/java/base/datatype/IntegerChanger.java
@@ -0,0 +1,44 @@
+package com.brianway.learning.java.base.datatype;
+
+import java.lang.reflect.Field;
+
+/**
+ * Created by brian on 16/11/1.
+ *
+ * 涉及到的知识点:
+ * 1.java 的参数传递都是值传递
+ * 2.Integer的内部实现(value,缓存,等等)
+ * 3.反射操作(可访问性)
+ * 4.自动装箱和拆箱
+ *
+ * 参考博客 http://www.voidcn.com/blog/zgwangbo/article/p-6101689.html
+ */
+public class IntegerChanger {
+
+    public static void main(String[] args) {
+        Integer a = 1, b = 2;
+        System.out.println("before swap a = " + a + ", b = " + b);
+        swap(a, b);
+        System.out.println("after swap a = " + a + ", b = " + b);
+
+        Integer c = 1;
+        System.out.println("(警告:Integer缓存被改了,代码里:Integer c = 1;) 实际c=" + c);
+    }
+
+    public static void swap(Integer i1, Integer i2) {
+        try {
+            Field f = Integer.class.getDeclaredField("value");
+            f.setAccessible(true);
+
+            int tmp = i1;
+            f.setInt(i1, i2);
+            f.setInt(i2, tmp);
+
+        } catch (NoSuchFieldException e) {
+            e.printStackTrace();
+        } catch (IllegalAccessException e) {
+            e.printStackTrace();
+        }
+
+    }
+}
diff --git a/java-base/src/main/java/com/brianway/learning/java/base/datatype/NumberEquation.java b/java-base/src/main/java/com/brianway/learning/java/base/datatype/NumberEquation.java
@@ -0,0 +1,22 @@
+package com.brianway.learning.java.base.datatype;
+
+/**
+ * Created by brian on 16/11/10.
+ *
+ * 包装类的“==”运算在不遇到算术运算的情况下不会自动拆箱;
+ * 包装类的equals()方法不处理数据转型.
+ */
+public class NumberEquation {
+    public static void main(String[] args) {
+        Integer i = 42;
+        Long l = 42l;
+        Double d = 42.0;
+
+        System.out.println(i.equals(d)); // false
+        System.out.println(d.equals(l)); // false
+        System.out.println(i.equals(l)); // false
+        System.out.println(l.equals(42L)); // true
+    }
+}
+
+// (i == l),(i == d),(l == d)会出现编译错误
diff --git a/java-base/src/main/java/com/brianway/learning/java/base/innerclass/ClassCreator.java b/java-base/src/main/java/com/brianway/learning/java/base/innerclass/ClassCreator.java
@@ -0,0 +1,16 @@
+package com.brianway.learning.java.base.innerclass;
+
+/**
+ * Created by brian on 16/11/10.
+ *
+ * 创建内部类的测试类
+ */
+public class ClassCreator {
+    public static void main(String[] args) {
+        //在其他类里创建非静态内部类和静态内部类
+        EnclosingOne eo = new EnclosingOne();
+        EnclosingOne.InsideOne io = eo.new InsideOne();
+        EnclosingOne.InsideTwo it = new EnclosingOne.InsideTwo();
+    }
+
+}
diff --git a/java-base/src/main/java/com/brianway/learning/java/base/innerclass/EnclosingOne.java b/java-base/src/main/java/com/brianway/learning/java/base/innerclass/EnclosingOne.java
@@ -0,0 +1,21 @@
+package com.brianway.learning.java.base.innerclass;
+
+/**
+ * Created by brian on 16/11/10.
+ */
+public class EnclosingOne {
+
+    public class InsideOne {
+
+    }
+
+    static public class InsideTwo {
+
+    }
+
+    public static void main(String[] args) {
+        EnclosingOne eo = new EnclosingOne();
+        InsideOne io = eo.new InsideOne();
+        InsideTwo it = new InsideTwo();
+    }
+}

Original file line number	Diff line number	Diff line change
`@@ -4,14 +4,19 @@`
`4`	`4`	`* Created by Brian on 2016/4/14.`
`5`	`5`	`*/`
`6`	`6`	`public class FatherClass {`
	`7`	`+ protected static int count = 10;`
`7`	`8`	`private String name;`
`8`	`9`
	`10`	`+ static {`
	`11`	`+ System.out.println("父类的静态属性count初始化:" + count);`
	`12`	`+ }`
	`13`	`+`
`9`	`14`	`public FatherClass() {`
`10`	`15`	`System.out.println("执行了父类的无参构造方法");`
`11`	`16`	`}`
`12`	`17`
`13`	`18`	`public FatherClass(String name) {`
`14`	`19`	`this.name = name;`
`15`		`- System.out.println("执行了父类的构造方法FatherClass(String name)");`
	`20`	`+ System.out.println("执行了父类的构造方法FatherClass(String name) " + name);`
`16`	`21`	`}`
`17`	`22`	`}`