在java.lang.reflect包中有三个类Field、Method和Constructor分别用来描述类的域、方法和构造器。三者都有一个getName的方法，用来返回项目的名称。
Field类有一个getType方法，用来返回描述域所属类型的Class对象。
Method 和Constructor 类有能够报告参数类型的方法，Method类还有可以报告返回类型的方法。
这三个类还有一个getModifiers的方法，它将返回一个整型数值，用不同的位开关描述public和static这用的修饰符使用状况。调用Modifier类的相应方法，并对返回的整型数值进行分析，还可以利用Modifier.toString方法将修饰符打印出来。
package reflection;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Scanner;
/**
* This program uses reflection to print all features of a class
*/
public class ReflectionTest {
public static void main(String[] args) {
String name;
if(args.length > 0) {
name = args[0];
} else {
Scanner in = new Scanner(System.in);
System.out.println("Enter class name (e.g. java.util.Date):");
name = in.next();
}
try {
//print class name and superclass name (if != Object)
Class cl = Class.forName(name);
Class supercl = cl.getSuperclass();
String modifiers = Modifier.toString(cl.getModifiers());
if(modifiers.length() > 0) {
System.out.print(modifiers + " ");
}
System.out.print("class " + name);
if(supercl != null && supercl != Object.class)
System.out.print(" extends " + supercl.getName());
System.out.print("\n{\n");
printConstructor(cl);
System.out.println();
printMethods(cl);
System.out.println();
printFields(cl);
System.out.println("}");
} catch(ClassNotFoundException e) {
e.printStackTrace();
}
System.exit(0);
}
/**
* Prints all constructors of a class
*/
public static void printConstructor(Class cl) {
Constructor[] constructors = cl.getDeclaredConstructors();
for(Constructor c : constructors) {
String name = c.getName();
System.out.print(" ");
String modifiers = Modifier.toString(c.getModifiers());
if(modifiers.length() > 0)
System.out.print(modifiers + " ");
System.out.print(name + "(");
//print parameter types
Class[] paramTypes = c.getParameterTypes();
for(int j = 0; j < paramTypes.length; j++) {
if(j > 0)
System.out.print(", ");
System.out.print(paramTypes[j].getName());
}
System.out.println(");");
}
}
/**
* Prints all methods of a class
*/
public static void printMethods(Class cl) {
Method[] methods = cl.getDeclaredMethods();
for(Method m : methods) {
Class retType = m.getReturnType();
String name = m.getName();
System.out.print(" ");
//print modifiers, return type and method name
String modifiers = Modifier.toString(m.getModifiers());
if(modifiers.length() > 0) {
System.out.print(modifiers + " ");
}
System.out.print(retType.getName() + " " + name + "(");
//print parameter types
Class[] paramTypes = m.getParameterTypes();
for(int j = 0; j < paramTypes.length; j++) {
if(j > 0)
System.out.print(", ");
System.out.print(paramTypes[j].getName());
}
System.out.println(");");
}
}
/**
* Prints all fields of a class
*/
public static void printFields(Class cl) {
Field[] fields = cl.getDeclaredFields();
for(Field f : fields) {
Class type = f.getType();
String name = f.getName();
System.out.print(" ");
String modifiers = Modifier.toString(f.getModifiers());
if(modifiers.length() > 0) {
System.out.print(modifiers + " ");
System.out.println(type.getName() + " " + name + ";");
}
}
}
}
编译并执行：
"C:\Program Files\Java\jdk1.8.0_131\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2018.2.1\lib\idea_rt.jar=63065:C:\Program Files\JetBrains\IntelliJ IDEA 2018.2.1\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.8.0_131\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_131\jre\lib\rt.jar;D:\IdeaProjects\JavaStudy\target\classes;E:\maven\repository\net\sf\json-lib\json-lib\2.4\json-lib-2.4-jdk15.jar;E:\maven\repository\commons-beanutils\commons-beanutils\1.8.0\commons-beanutils-1.8.0.jar;E:\maven\repository\commons-collections\commons-collections\3.2.1\commons-collections-3.2.1.jar;E:\maven\repository\commons-lang\commons-lang\2.5\commons-lang-2.5.jar;E:\maven\repository\commons-logging\commons-logging\1.1.1\commons-logging-1.1.1.jar;E:\maven\repository\net\sf\ezmorph\ezmorph\1.0.6\ezmorph-1.0.6.jar" reflection.ReflectionTest
Enter class name (e.g. java.util.Date):
java.util.Date
public class java.util.Date
{
public java.util.Date(int, int, int, int, int, int);
public java.util.Date(java.lang.String);
public java.util.Date();
public java.util.Date(long);
public java.util.Date(int, int, int);
public java.util.Date(int, int, int, int, int);
public boolean after(java.util.Date);
public boolean before(java.util.Date);
public boolean equals(java.lang.Object);
public java.lang.String toString();
public int hashCode();
public java.lang.Object clone();
public int compareTo(java.util.Date);
public volatile int compareTo(java.lang.Object);
private void readObject(java.io.ObjectInputStream);
private void writeObject(java.io.ObjectOutputStream);
private final sun.util.calendar.BaseCalendar$Date normalize();
private final sun.util.calendar.BaseCalendar$Date normalize(sun.util.calendar.BaseCalendar$Date);
public static long parse(java.lang.String);
public int getDate();
public static java.util.Date from(java.time.Instant);
public long getTime();
public void setTime(long);
private static final java.lang.StringBuilder convertToAbbr(java.lang.StringBuilder, java.lang.String);
private final sun.util.calendar.BaseCalendar$Date getCalendarDate();
private static final sun.util.calendar.BaseCalendar getCalendarSystem(long);
private static final sun.util.calendar.BaseCalendar getCalendarSystem(int);
private static final sun.util.calendar.BaseCalendar getCalendarSystem(sun.util.calendar.BaseCalendar$Date);
public int getDay();
public int getHours();
private static final synchronized sun.util.calendar.BaseCalendar getJulianCalendar();
static final long getMillisOf(java.util.Date);
public int getMinutes();
public int getMonth();
public int getSeconds();
private final long getTimeImpl();
public int getTimezoneOffset();
public int getYear();
public void setDate(int);
public void setHours(int);
public void setMinutes(int);
public void setMonth(int);
public void setSeconds(int);
public void setYear(int);
public java.lang.String toGMTString();
public java.time.Instant toInstant();
public java.lang.String toLocaleString();
public static long UTC(int, int, int, int, int, int);
private static final sun.util.calendar.BaseCalendar gcal;
private static sun.util.calendar.BaseCalendar jcal;
private transient long fastTime;
private transient sun.util.calendar.BaseCalendar$Date cdate;
private static int defaultCenturyStart;
private static final long serialVersionUID;
private static final [Ljava.lang.String; wtb;
private static final [I ttb;
}
进程完成，退出码 0