java 高新技术 总结(一)

public static void main(String[] args) {
System.out.println(sum(1,2,3));
System.out.println(sumfor(1,2,3));
}
/**
* 多变参数
* @param i
* @param args
* @return
*/
public static int sum(int i ,int ...args){
int sum = 0;
for (int j = 0; j < args.length; j++) {
sum+=args[i];
}
return sum;
}
/**
* 增强for循环
* @param i
* @param args
* @return
*/
public static int sumfor(int i ,int ...args){
int sum = i;//注意此处
for (int arg : args) {
sum+=arg;
}
return sum;
}

public static void main(String[] args) {

System.out.println(WeekDays.SUN);
//		System.out.println(WeekDays.SUN.name());
//		System.out.println(WeekDays.SUN.name().toString());
//		System.out.println(WeekDays.SUN.ordinal());
//		System.out.println(WeekDays.valueOf("SUN").name());
//		System.out.println(WeekDays.values().length);

}

public enum WeekDays{

SUN(1),MON(2,3),TUS,WED,THI,FRI,STA;
private WeekDays() {
System.out.println("frist");

}
private WeekDays(int day) {
System.out.println("second");
}
private WeekDays(int day,int name) {
System.out.println("third");
}

}
/**
* 带抽象方法
* 有构造方法
* @author Administrator
*
*/
public enum Light{

RED(20){

@Override
public Light getLight() {
// TODO Auto-generated method stub
return null;
}

},
GREEN(40){

@Override
public Light getLight() {
// TODO Auto-generated method stub
return null;
}

};
public abstract Light getLight();
private int time;
private Light(int time){
this.time  = time;
};

}

/**
* 反射辅助类
* @author JiaRH
*
*/
public class FieldReflect {

private int x = 0;
public int y = 0;

public String aa1="bbbaaa";
public String aa2="bbbaaa";
public String aa3="bbbaaa";
public FieldReflect(int x, int y) {
super();
this.x = x;
this.y = y;
}

@Override
public String toString() {
// TODO Auto-generated method stub
return aa1+"=="+aa2+"=="+aa3;

}
}

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class Reflect {

public static void main(String[] args) {
String str1 = "abc";
Class cl1 = str1.getClass();
Class cl2 = String.class;
try {
/**
* 反射基本方法
*/
Class cl3 = Class.forName("java.lang.String");
System.out.println(cl1==cl2);
System.out.println(cl1==cl3);
System.out.println(cl2==cl3);
System.out.println(int.class == Integer.TYPE );
System.out.println(cl1.isPrimitive());
System.out.println(cl2.isPrimitive());
System.out.println(cl3.isPrimitive());
System.out.println(Integer.class.isPrimitive());
System.out.println(int.class.isPrimitive());
/**
*
* 获取 构造方法，并实例新的对象
*/
Constructor constructor = String.class.getConstructor(StringBuffer.class);
String str2 = (String)constructor.newInstance(new StringBuffer("abc"));
System.out.println(str2.charAt(2));
/**
* 字段
* 获取成员变量的值
*/
FieldReflect f1 = new FieldReflect(2, 5);
FieldReflect f2 = new FieldReflect(2, 6);
//获取成员变量对象
Field ff1 = f1.getClass().getField("y");
Field ff2 = f1.getClass().getField("y");
//取值
System.out.println(ff1.get(f1)+"");//注意获取值的方法
System.out.println(ff2.get(f2)+"");

/**
* 获取私有的成员变量
* (暴力反射)
*/
Field ff3 = f1.getClass().getDeclaredField("x");
ff3.setAccessible(true);
System.out.println(ff3.get(f1)+"");

/**
* 利用反射改变值
* 将f1对象中所有的成员变量中含有的a变为b
*/
Field[] fields = f1.getClass().getFields();

for (Field field: fields) {
if (field.getType()==String.class) {
String priValue = (String) field.get(f1);
String newValue = priValue.replace('a', 'b');
field.set(f1, newValue);

}
}
System.out.println(f1);

/**
* 获取方法
* 调用方法
*/
//new String().charAt(index)
Method methodCharat=String.class.getMethod("charAt", int.class);
System.out.println(methodCharat.invoke(str2, 1));
//System.out.println(methodCharat.invoke(null, 1));//表明是一个静态方法

} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchMethodException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InstantiationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchFieldException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}
}

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

//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"});