java反射

反射 java反射

获取类 class c = Class.forName("com.example.TestClass"); 获取类权限 ++public++ ++private++ ++static++ System.out.print(Modifier.toString(c.getModifiers())); 获取类名 System.out.print(c.getSimpleName()); 获取所有属性 Field[] fields = c.getDeclaredFields(); 属性权限 System.out.print(Modifier.toString(f.getModifiers()) + " "); 属性返回类型 System.out.print(f.getType().getSimpleName() + " "); 属性名 System.out.print(f.getName() + " "); 获取所有方法 Method[] methods = c.getMethods(); System.out.print(Modifier.toString(method.getModifiers())); System.out.print(" " + method.getReturnType().getSimpleName()); System.out.print(" " + method.getName()); Class<?>[] parameters = method.getParameterTypes(); 指定方法 c = Class.forName("com.example.TestClass"); o = c.newInstance(); Method method = c.getDeclaredMethod("method2", String.class); method.setAccessible(true); System.out.print(" " + (String) method.invoke(o, "123")); 指定属性 Field f = c.getField("field1"); f.setAccessible(true); System.out.println("" + f.get(o)); 构造方法 System.out.println("无参构造方法:"); o = c.newInstance(); System.out.println("有参构造方法:"); Constructor<?> oo = c.getConstructor(String.class);

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例子:通过反射使用SystemProperties的api

package com.sprd.ext; import android.text.TextUtils; import java.lang.reflect.Method; import android.os.SystemProperties; /** * Created by SPRD on 6/13/17. */ public class SystemPropertiesUtils { private static final String TAG = "SystemPropertiesUtils"; private static Class<?> mClassType = null; private static Method mGetMethod = null; private static Method mGetIntMethod = null; private static Method mGetBooleanMethod = null; private static Class<?> getSystemPropertiesClass() throws ClassNotFoundException { if (mClassType == null) { mClassType = Class.forName("android.os.SystemProperties"); } return mClassType; } private static Method getMethod() throws Exception { if (mGetMethod == null) { Class clazz = getSystemPropertiesClass(); mGetMethod = clazz.getDeclaredMethod("get", String.class); } return mGetMethod; } private static Method getIntMethod() throws Exception { if (mGetIntMethod == null) { Class clazz = getSystemPropertiesClass(); mGetIntMethod = clazz.getDeclaredMethod("getInt", String.class, int.class); } return mGetIntMethod; } private static Method getBooleanMethod() throws Exception { if (mGetBooleanMethod == null) { Class clazz = getSystemPropertiesClass(); mGetBooleanMethod = clazz.getDeclaredMethod("getBoolean", String.class, boolean.class); } return mGetBooleanMethod; } public static String get(String key, String def) { try { String value = (String) getMethod().invoke(null, key); if (!TextUtils.isEmpty(value)) { return value; } } catch (Exception e) { LogUtils.d(TAG, "Unable to read system properties"); } return def; } public static int getInt(String key, int def) { int value = def; try { value = (int) getIntMethod().invoke(null, key, def); } catch (Exception e) { LogUtils.d(TAG, "Unable to read system properties"); } return value; } public static boolean getBoolean(String key, boolean def) { boolean value = def; try { value = (Boolean) getBooleanMethod().invoke(null, key, def); } catch (Exception e) { LogUtils.d(TAG, "Unable to read system properties"); } return value; } }