Java基础

标签：java

Java提供了强大的反射机制，可以通过Class类获取任何的字段，方法，构造函数，并对它们进行修改或者调用。下面的例子演示了怎么通过java.lang.reflect包下的类获得String类的所有字段，构造函数，方法。

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.Parameter;

public class Reflection {
	@SuppressWarnings("rawtypes")
	public static void main(String[] args) {
		Class<String> string = String.class;
		Field[] fields = string.getDeclaredFields();
		Method[] methods = string.getDeclaredMethods();
		Constructor[] constructors = string.getConstructors();
		String name = "";
		String typeName = "";
		String visibility = "";

		System.out.println("------------Field-------------------------");
		// 遍历字段，打印出它的作用域，限定词，字段名
		for (Field f : fields) {
			visibility = f.getGenericType().getTypeName();
			name = f.getName();
			typeName = f.getType().getTypeName();
			visibility = isVisibility(f.getModifiers());
			System.out.println(visibility + typeName + "  " + name + ";");
		}

		String returnType = "";
		String params = "";

		System.out.println("-----------constructor----------------------------");
		// 遍历构造函数
		for (Constructor c : constructors) {
			visibility = isVisibility(c.getModifiers());
			name = c.getName();
			params= getParams(c.getParameters());

			System.out.println(visibility + name + " ("
					+ params + ") ");
		}

		System.out.println("-----------method----------------------------------");
		// 遍历函数，打印出它的作用域，返回类型，函数名，传递的参数
		for (Method m : methods) {
			name = m.getName();

			returnType = m.getReturnType().getTypeName();
			params = getParams(m.getParameters());
			visibility = isVisibility(m.getModifiers());
			System.out.println(visibility + returnType + "  " + name + " ("
					+ params + ") ");
		}
	}

	private static String getParams(Parameter[] parameters) {
		// TODO Auto-generated method stub
		String params = "";
		for (Parameter p : parameters) {
			params += p.getType().getTypeName() + " " + p.getName() + ",";
		}
		if (params.length() > 0)
			params = params.substring(0, params.length() - 1);
		return params;
	}

	/**
	 * 查询字段或方法的访问权限
	 * 
	 * @param modifiers
	 * @return 字段/方法的作用域
	 */
	private static String isVisibility(int modifiers) {
		// TODO Auto-generated method stub
		String visibility = "";
		if (Modifier.isPrivate(modifiers)) {
			visibility += "private ";
		}
		if (Modifier.isProtected(modifiers)) {
			visibility += "protected ";
		}

		if (Modifier.isPublic(modifiers)) {
			visibility += "public ";
		}
		if (Modifier.isAbstract(modifiers)) {
			visibility += "abstract ";
		}
		if (Modifier.isStatic(modifiers)) {
			visibility += "static ";
		}
		if (Modifier.isFinal(modifiers)) {
			visibility += "final ";
		}
		if (Modifier.isNative(modifiers)) {
			visibility += "native ";
		}

		if (Modifier.isVolatile(modifiers)) {
			visibility += "volatile ";
		}
		if (Modifier.isSynchronized(modifiers)) {
			visibility += "synchronized ";
		}

		if (Modifier.isTransient(modifiers)) {
			visibility += "transient ";
		}
		return visibility;
	}
}

Java基础

标签：java

原文地址：http://blog.csdn.net/u013769320/article/details/45273355