程序清单－打印一个类的全部信息

这个程序将提醒用户输入类名，然后输入类中所有方法和构造器的签名，以及全部域名。
如：

请输入类名：java.lang.Doublepublic final  class java.lang.Double extends java.lang.Number{   public    java.lang.Double(double);   public    java.lang.Double(java.lang.String);   public    boolean equals(java.lang.Object);   public static    java.lang.String toString(double);   public    java.lang.String toString();   public    int hashCode();   public static native    long doubleToRawLongBits(double);   public static    long doubleToLongBits(double);   public static native    double longBitsToDouble(long);   public    int compareTo(java.lang.Double);   public volatile    int compareTo(java.lang.Object);   public    byte byteValue();   public    short shortValue();   public    int intValue();   public    long longValue();   public    float floatValue();   public    double doubleValue();   public static    java.lang.Double valueOf(double);   public static    java.lang.Double valueOf(java.lang.String);   public static    java.lang.String toHexString(double);   public static    int compare(double,  double);   public static    boolean isNaN(double);   public    boolean isNaN();   public static    boolean isInfinite(double);   public    boolean isInfinite();   public static    double parseDouble(java.lang.String);public static final    double POSITIVE_INFINITY;   public static final    double NEGATIVE_INFINITY;   public static final    double NaN;   public static final    double MAX_VALUE;   public static final    double MIN_NORMAL;   public static final    double MIN_VALUE;   public static final    int MAX_EXPONENT;   public static final    int MIN_EXPONENT;   public static final    int SIZE;   public static final    java.lang.Class TYPE;   private final    double value;   private static final    long serialVersionUID;}

程序源代码：

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("请输入类名：");            name = in.next();        }        try {            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");            printConstructors(cl);            System.out.println();            printMethods(cl);            System.out.println();            printFields(cl);            System.out.println("}");        } catch (ClassNotFoundException e) {            e.printStackTrace();        }    }    /**     * 输出构造函数     * @param cl     */    public static void printConstructors(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+"(");            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(");");        }    }    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("   ");            String modifiers = Modifier.toString(m.getModifiers());            if (modifiers.length()>0)  System.out.print(modifiers+"    ");            System.out.print(retType.getName()+" "+name+"(");            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(");");        }    }    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+";");        }    }}