java中的反射

package reflect.test;

import java.lang.reflect.Array;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Arrays;

public class ReflectTest {

/**
* @param args
*/
public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
String str1 = “abc”;
Class cls1 = str1.getClass();
Class cls2 = String.class;
Class cls3 = Class.forName(“java.lang.String”);
System.out.println(cls1 == cls2);
System.out.println(cls1 == cls3);

System.out.println(cls1.isPrimitive());
System.out.println(int.class.isPrimitive());
System.out.println(int.class == Integer.class);
System.out.println(int.class == Integer.TYPE);
System.out.println(int[].class.isPrimitive());
System.out.println(int[].class.isArray());

//new String(new StringBuffer(“abc”));
Constructor constructor1 = String.class.getConstructor(StringBuffer.class);
String str2 = (String)constructor1.newInstance(/*”abc”*/new StringBuffer(“abc”));
System.out.println(str2.charAt(2));

ReflectPoint pt1 = new ReflectPoint(3,5);
Field fieldY = pt1.getClass().getField(“y”);
//fieldY的值是多少?是5,错!fieldY不是对象身上的变量,而是类上,要用它去取某个对象上对应的值
System.out.println(fieldY.get(pt1));
Field fieldX = pt1.getClass().getDeclaredField(“x”);
fieldX.setAccessible(true);
System.out.println(fieldX.get(pt1));

changeStringValue(pt1);
System.out.println(pt1);

Method methodCharAt = String.class.getMethod(“charAt”, int.class);
System.out.println(methodCharAt.invoke(str1, 1));
System.out.println(methodCharAt.invoke(str1, new Object[]{0}));

//TestArguments.main(new String[]{“111″,”222″,”333”});
String startingClassName = args[0];
Method mainMethod = Class.forName(startingClassName).getMethod(“main”, String[].class);
//mainMethod.invoke(null, new Object[]{new String[]{“111″,”222″,”333”}});
mainMethod.invoke(null, (Object)new String[]{“111″,”222″,”333”});

int [] a1 = new int[]{1,2,3};
int [] a2 = new int[4];
int[][] a3 = new int[2][3];
String [] a4 = new String[]{“a”,”b”,”c”};
System.out.println(a1.getClass() == a2.getClass());
/*System.out.println(a1.getClass() == a3.getClass());
System.out.println(a2.getClass() == a3.getClass());*/
System.out.println(a4.getClass().getName());
System.out.println(a1.getClass().getName());
System.out.println(a1.getClass().getSuperclass().getName());
System.out.println(a4.getClass().getSuperclass().getName());

Object aObj1 = a1;
Object aObj2 = a4;
//Object[] aObj3 = a1;
Object[] aObj4 = a3;
Object[] aObj5 = a4;

System.out.println(a1);
System.out.println(a4);
System.out.println(Arrays.asList(a1));
System.out.println(Arrays.asList(a4));

printObject(a4);
printObject(a1);

printObject(“xyz”);
}

private static void printObject(Object obj) {
Class clazz = obj.getClass();
if(clazz.isArray()){
int len = Array.getLength(obj);
for(int i=0;i<len;i++){
System.out.println(Array.get(obj, i));
}
}else{
System.out.println(obj);
}

}

private static void changeStringValue(Object obj) throws Exception {
Field[] fields = obj.getClass().getFields();
for(Field field : fields){
//if(field.getType().equals(String.class)){
if(field.getType() == String.class){
String oldValue = (String)field.get(obj);
String newValue = oldValue.replace(‘b’, ‘a’);
field.set(obj, newValue);
}
}

}

}
class TestArguments{
public static void main(String[] args){
for(String arg : args){
System.out.println(arg);
}
}
}

———————————–

package cn.itcast.day1;

import java.io.FileInputStream;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.Properties;

public class ReflectTest2 {

/**
* @param args
*/
public static void main(String[] args) throws Exception{
// TODO Auto-generated method stub
/*getRealPath();//金山词霸/内部
一定要记住用完整的路径,但完整的路径不是硬编码,而是运算出来的。*/
//InputStream ips = new FileInputStream(“config.properties”);

//InputStream ips = ReflectTest2.class.getClassLoader().getResourceAsStream(“cn/itcast/day1/config.properties”);
//InputStream ips = ReflectTest2.class.getResourceAsStream(“resources/config.properties”);
InputStream ips = ReflectTest2.class.getResourceAsStream(“/cn/itcast/day1/resources/config.properties”);

Properties props = new Properties();
props.load(ips);
ips.close();
String className1 = props.getProperty(“className”);
Collection collections = (Collection)Class.forName(className1).newInstance();

//Collection collections = new HashSet();
ReflectPoint pt1 = new ReflectPoint(3,3);
ReflectPoint pt2 = new ReflectPoint(5,5);
ReflectPoint pt3 = new ReflectPoint(3,3);

collections.add(pt1);
collections.add(pt2);
collections.add(pt3);
collections.add(pt1);

//pt1.y = 7;
//collections.remove(pt1);

System.out.println(collections.size());
}

}

 

———————————————-

package cn.itcast.day1;

import java.util.Date;

public class ReflectPoint {
private Date birthday = new Date();

private int x;
public int y;
public String str1 = “ball”;
public String str2 = “basketball”;
public String str3 = “itcast”;

public ReflectPoint(int x, int y) {
super();
this.x = x;
this.y = y;
}

@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + x;
result = prime * result + y;
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
final ReflectPoint other = (ReflectPoint) obj;
if (x != other.x)
return false;
if (y != other.y)
return false;
return true;
}
@Override
public String toString(){
return str1 + “:” + str2 + “:” + str3;
}
public int getX() {
return x;
}
public void setX(int x) {
this.x = x;
}
public int getY() {
return y;
}
public void setY(int y) {
this.y = y;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
}

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