🔖 反射示例

dunwu · dunwu · commit 93d5c1fc30c7 · 2018-06-05T14:26:38.000+08:00
diff --git a/codes/advanced/src/test/java/io/github/dunwu/javase/reflect/ReflectClassTest.java b/codes/advanced/src/test/java/io/github/dunwu/javase/reflect/ReflectClassTest.java
@@ -0,0 +1,105 @@
+package io.github.dunwu.javase.reflect;
+
+import java.lang.reflect.Field;
+import java.util.HashSet;
+import java.util.Set;
+import org.junit.Test;
+
+/**
+ * @author Zhang Peng
+ * @date 2018/6/5
+ */
+public class ReflectClassTest {
+    enum E {A, B}
+
+    /**
+     * getClass() 示例
+     */
+    @Test
+    public void demo1() {
+        Class c = "foo".getClass();
+        System.out.println(c.getCanonicalName());
+
+        Class c2 = ReflectClassTest.E.A.getClass();
+        System.out.println(c2.getCanonicalName());
+
+        byte[] bytes = new byte[1024];
+        Class c3 = bytes.getClass();
+        System.out.println(c3.getCanonicalName());
+
+        Set<String> set = new HashSet<>();
+        Class c4 = set.getClass();
+        System.out.println(c4.getCanonicalName());
+    }
+
+    /**
+     * .class 示例
+     */
+    @Test
+    public void demo2() {
+        boolean b;
+        // Class c = b.getClass(); // 编译错误
+        Class c1 = boolean.class;
+        System.out.println(c1.getCanonicalName());
+
+        Class c2 = java.io.PrintStream.class;
+        System.out.println(c2.getCanonicalName());
+
+        Class c3 = int[][][].class;
+        System.out.println(c3.getCanonicalName());
+    }
+
+    /**
+     * forName() 示例
+     */
+    @Test
+    public void demo3() {
+        try {
+            Class c1 = Class.forName("io.github.dunwu.javase.reflect.ReflectClassTest");
+            System.out.println(c1.getCanonicalName());
+
+            Class c2 = Class.forName("[D");
+            System.out.println(c2.getCanonicalName());
+
+            Class c3 = Class.forName("[[Ljava.lang.String;");
+            System.out.println(c3.getCanonicalName());
+        } catch (ClassNotFoundException e) {
+            e.printStackTrace();
+        }
+    }
+
+    /**
+     * .TYPE 示例
+     */
+    @Test
+    public void demo4() {
+        Class c1 = Double.TYPE;
+        System.out.println(c1.getCanonicalName());
+
+        Class c2 = Void.TYPE;
+        System.out.println(c2.getCanonicalName());
+    }
+
+    @Test
+    public void demo5() throws NoSuchFieldException {
+        Class c1 = javax.swing.JButton.class.getSuperclass();
+        System.out.println(c1.getCanonicalName());
+
+        Class<?>[] classes = Character.class.getClasses();
+        for (Class c : classes) {
+            System.out.println(c.getCanonicalName());
+        }
+
+        Class<?>[] classes2 = Character.class.getDeclaredClasses();
+        for (Class c : classes2) {
+            System.out.println(c.getCanonicalName());
+        }
+
+        Field f = System.class.getField("out");
+        Class c2 = f.getDeclaringClass();
+        System.out.println(c2.getCanonicalName());
+
+        Class c3 = Thread.State.class.getEnclosingClass();
+        System.out.println(c3.getCanonicalName());
+    }
+}
