🔖 反射示例

dunwu · dunwu · commit 40279746b877 · 2018-06-05T17:42:03.000+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
@@ -1,7 +1,11 @@
 package io.github.dunwu.javase.reflect;
 
+import java.lang.reflect.Constructor;
 import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
+import java.util.ArrayList;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
 import org.junit.Test;
 
@@ -102,4 +106,31 @@ public void demo5() throws NoSuchFieldException {
         Class c3 = Thread.State.class.getEnclosingClass();
         System.out.println(c3.getCanonicalName());
     }
+
+    @Test
+    public void demo06() {
+        ArrayList arrayList = new ArrayList();
+        if (arrayList instanceof List) {
+            System.out.println("ArrayList is List");
+        }
+        if (List.class.isInstance(arrayList)) {
+            System.out.println("ArrayList is List");
+        }
+    }
+
+    @Test
+    public void demo07()
+        throws IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException {
+        Class<?> c1 = String.class;
+        Object str1 = c1.newInstance();
+        System.out.println(str1.getClass().getCanonicalName());
+
+        //获取String所对应的Class对象
+        Class<?> c2 = String.class;
+        //获取String类带一个String参数的构造器
+        Constructor constructor = c2.getConstructor(String.class);
+        //根据构造器创建实例
+        Object obj = constructor.newInstance("bbb");
+        System.out.println(obj.getClass().getCanonicalName());
+    }
 }
diff --git a/codes/advanced/src/test/java/io/github/dunwu/javase/reflect/ReflectConstructorTest.java b/codes/advanced/src/test/java/io/github/dunwu/javase/reflect/ReflectConstructorTest.java
@@ -0,0 +1,30 @@
+package io.github.dunwu.javase.reflect;
+
+import java.io.FileOutputStream;
+import java.lang.reflect.Constructor;
+import org.junit.Test;
+
+/**
+ * @author Zhang Peng
+ * @date 2018/6/5
+ */
+public class ReflectConstructorTest {
+    @Test
+    public void demo1() throws NoSuchMethodException {
+        Constructor<?>[] constructors1 = FileOutputStream.class.getDeclaredConstructors();
+        System.out.println("FileOutputStream getDeclaredConstructors 清单（数量 = " + constructors1.length + "）：");
+        for (Constructor c : constructors1) {
+            System.out.println(c);
+        }
+
+        Constructor<?>[] constructors2 = FileOutputStream.class.getConstructors();
+        System.out.println("FileOutputStream getConstructors 清单（数量 = " + constructors2.length + "）：");
+        for (Constructor c : constructors2) {
+            System.out.println(c);
+        }
+
+        System.out.println("====================");
+        Constructor constructor = FileOutputStream.class.getConstructor(String.class, boolean.class);
+        System.out.println(constructor);
+    }
+}
diff --git a/codes/advanced/src/test/java/io/github/dunwu/javase/reflect/ReflectFieldTest.java b/codes/advanced/src/test/java/io/github/dunwu/javase/reflect/ReflectFieldTest.java
@@ -0,0 +1,37 @@
+package io.github.dunwu.javase.reflect;
+
+import java.lang.reflect.Field;
+import java.util.List;
+import org.junit.Test;
+
+/**
+ * @author Zhang Peng
+ * @date 2018/6/5
+ */
+public class ReflectFieldTest {
+    class FieldSpy<T> {
+        public boolean[][] b = {{ false, false }, { true, true } };
+        public String name  = "Alice";
+        public List<Integer> list;
+        public T val;
+    }
+
+    @Test
+    public void demo1() {
+        try {
+            Field f1 = FieldSpy.class.getField("b");
+            System.out.format("Type: %s%n", f1.getType());
+
+            Field f2 = FieldSpy.class.getField("name");
+            System.out.format("Type: %s%n", f2.getType());
+
+            Field f3 = FieldSpy.class.getField("list");
+            System.out.format("Type: %s%n", f3.getType());
+
+            Field f4 = FieldSpy.class.getField("val");
+            System.out.format("Type: %s%n", f4.getType());
+        } catch (NoSuchFieldException x) {
+            x.printStackTrace();
+        }
+    }
+}
diff --git a/codes/advanced/src/test/java/io/github/dunwu/javase/reflect/ReflectMethodTest.java b/codes/advanced/src/test/java/io/github/dunwu/javase/reflect/ReflectMethodTest.java
@@ -0,0 +1,30 @@
+package io.github.dunwu.javase.reflect;
+
+import java.lang.reflect.Method;
+import org.junit.Test;
+
+/**
+ * @author Zhang Peng
+ * @date 2018/6/5
+ */
+public class ReflectMethodTest {
+    @Test
+    public void demo1() throws NoSuchMethodException {
+        // getDeclaredMethods()方法返回类或接口声明的所有方法，包括公共、保护、默认（包）访问和私有方法，但不包括继承的方法。
+        Method[] methods1 = Thread.class.getDeclaredMethods();
+        System.out.println("Thread getDeclaredMethods 清单（数量 = " + methods1.length + "）：");
+        for (Method m : methods1) {
+            System.out.println(m);
+        }
+
+        // getMethods() 方法返回某个类的所有公用（public）方法，包括其继承类的公用方法。
+        Method[] methods2 = Thread.class.getMethods();
+        System.out.println("Thread getMethods 清单（数量 = " + methods2.length + "）：");
+        for (Method m : methods2) {
+            System.out.println(m);
+        }
+
+        Method method = Thread.class.getMethod("join", long.class, int.class);
+        System.out.println(method);
+    }
+}
