通过反射输入一个类，打印出类中所有元素

代码如下：

import java.util.*;import java.lang.reflect.*;/**反射---输入一个类，打印出类中所有元素reflect包中有三个描述类元素的类：Field、Method、Constructor*/public class Sample{    public static void main(String[] args)    {        String name;//收集用户输入的类        if(args.length > 0)        {            name = args[0];        }        else        {            Scanner in = new Scanner(System.in);            System.out.println("Enter class name!");            name = in.next();        }        try        {            Class cl = Class.forName(name);//获得用户输入类的Class类型            Class supercl = cl.getSuperclass();//获得用户输入类的超类            String modifiers = Modifier.toString(cl.getModifiers());//获得修饰符数值后用Modifier类解释出来。            if(modifiers.length() > 0)            {                System.out.print(modifiers + " ");            }            System.out.print("class " + name);            if(supercl != null)//如果想排除掉顶级根：&& supercl != Object.class            {                System.out.print(" extends "+supercl.getName());            }            System.out.print("\n{\n");            printConstructors(cl);//获得构造函数            System.out.println();            printMethods(cl);//获得方法            System.out.println();            printFields(cl);//获得字段            System.out.println("}");        }        catch (ClassNotFoundException e)        {            e.printStackTrace();        }        System.exit(0);    }    public static void printConstructors(Class cl)    {        Constructor[] constructors = cl.getDeclaredConstructors();//获得构造函数列表        for(Constructor c : constructors)        {            String name = c.getName();//获得名字            System.out.print("  ");            String modifiers = Modifier.toString(c.getModifiers());//获得修饰符            if(modifiers.length() > 0)            {                System.out.print(modifiers+" ");            }            System.out.print(name+"(");            Class[] paramTypes = c.getParameterTypes();//获得参数类型列表            for(int j = 0;j < paramTypes.length; j++)            {                System.out.print(paramTypes[j].getName());                if( j < paramTypes.length-1)                {                    System.out.print(", ");                }            }            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++)            {                System.out.print(paramTypes[j].getName());                if( j < paramTypes.length-1)                {                    System.out.print(", ");                }            }            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+";");        }    }}/**输出类似结果：public final class java.util.Scanner extends java.lang.Object{  private java.util.Scanner(java.nio.file.Path, java.nio.charset.Charset);  public java.util.Scanner(java.io.InputStream, java.lang.String);  public java.util.Scanner(java.io.InputStream);  public java.util.Scanner(java.nio.file.Path);  private java.util.Scanner(java.lang.Readable, java.util.regex.Pattern);  private java.util.Scanner(java.io.File, java.nio.charset.CharsetDecoder);  public java.util.Scanner(java.io.File, java.lang.String);  public java.util.Scanner(java.io.File);  public java.util.Scanner(java.nio.file.Path, java.lang.String);  public java.util.Scanner(java.nio.channels.ReadableByteChannel, java.lang.String);  public java.util.Scanner(java.lang.Readable);  public java.util.Scanner(java.nio.channels.ReadableByteChannel);  public java.util.Scanner(java.lang.String);  public void remove();  public java.lang.String toString();  public boolean hasNext();  public boolean hasNext(java.lang.String);  public boolean hasNext(java.util.regex.Pattern);  public java.lang.String next();  public volatile java.lang.Object next();  public java.lang.String next(java.util.regex.Pattern);  public java.lang.String next(java.lang.String);  public void close();  public java.util.Scanner reset();  public double nextDouble();  public int nextInt(int);  public int nextInt();  public java.util.regex.MatchResult match();  public java.util.Scanner skip(java.util.regex.Pattern);  public java.util.Scanner skip(java.lang.String);  private void ensureOpen();  public java.util.Locale locale();  private static java.nio.charset.Charset toCharset(java.lang.String);  private static java.util.regex.Pattern boolPattern();  private void buildFloatAndDecimalPattern();  private java.lang.String buildIntegerPatternString();  private void cacheResult();  private void cacheResult(java.lang.String);  private void clearCaches();  private java.util.regex.Pattern decimalPattern();  public java.util.regex.Pattern delimiter();  public java.lang.String findInLine(java.util.regex.Pattern);  public java.lang.String findInLine(java.lang.String);  private java.lang.String findPatternInBuffer(java.util.regex.Pattern, int);  public java.lang.String findWithinHorizon(java.util.regex.Pattern, int);  public java.lang.String findWithinHorizon(java.lang.String, int);  private java.util.regex.Pattern floatPattern();  private java.lang.String getCachedResult();  private java.lang.String getCompleteTokenInBuffer(java.util.regex.Pattern);  public boolean hasNextBigDecimal();  public boolean hasNextBigInteger();  public boolean hasNextBigInteger(int);  public boolean hasNextBoolean();  public boolean hasNextByte(int);  public boolean hasNextByte();  public boolean hasNextDouble();  public boolean hasNextFloat();  public boolean hasNextInt(int);  public boolean hasNextInt();  public boolean hasNextLine();  public boolean hasNextLong(int);  public boolean hasNextLong();  public boolean hasNextShort();  public boolean hasNextShort(int);  private boolean hasTokenInBuffer();  private java.util.regex.Pattern integerPattern();  public java.io.IOException ioException();  private static java.util.regex.Pattern linePattern();  private static java.lang.Readable makeReadable(java.nio.channels.ReadableByteChannel, java.nio.charset.CharsetDecoder);  private static java.lang.Readable makeReadable(java.io.InputStream, java.nio.charset.Charset);  private static java.lang.Readable makeReadable(java.nio.channels.ReadableByteChannel);  private boolean makeSpace();  private java.lang.String matchPatternInBuffer(java.util.regex.Pattern);  public java.math.BigDecimal nextBigDecimal();  public java.math.BigInteger nextBigInteger();  public java.math.BigInteger nextBigInteger(int);  public boolean nextBoolean();  public byte nextByte();  public byte nextByte(int);  public float nextFloat();  public java.lang.String nextLine();  public long nextLong(int);  public long nextLong();  public short nextShort(int);  public short nextShort();  private java.lang.String processFloatToken(java.lang.String);  private java.lang.String processIntegerToken(java.lang.String);  public int radix();  private void readInput();  private boolean revertState(boolean);  private void revertState();  private void saveState();  private static java.util.regex.Pattern separatorPattern();  private void setRadix(int);  private void throwFor();  private static java.nio.charset.CharsetDecoder toDecoder(java.lang.String);  private void translateSavedIndexes(int);  public java.util.Scanner useDelimiter(java.lang.String);  public java.util.Scanner useDelimiter(java.util.regex.Pattern);  public java.util.Scanner useLocale(java.util.Locale);  public java.util.Scanner useRadix(int);  private void useTypeCache();  private java.nio.CharBuffer buf;  private static final int BUFFER_SIZE;  private int position;  private java.util.regex.Matcher matcher;  private java.util.regex.Pattern delimPattern;  private java.util.regex.Pattern hasNextPattern;  private int hasNextPosition;  private java.lang.String hasNextResult;  private java.lang.Readable source;  private boolean sourceClosed;  private boolean needInput;  private boolean skipped;  private int savedScannerPosition;  private java.lang.Object typeCache;  private boolean matchValid;  private boolean closed;  private int radix;  private int defaultRadix;  private java.util.Locale locale;  private sun.misc.LRUCache patternCache;  private java.io.IOException lastException;  private static java.util.regex.Pattern WHITESPACE_PATTERN;  private static java.util.regex.Pattern FIND_ANY_PATTERN;  private static java.util.regex.Pattern NON_ASCII_DIGIT;  private java.lang.String groupSeparator;  private java.lang.String decimalSeparator;  private java.lang.String nanString;  private java.lang.String infinityString;  private java.lang.String positivePrefix;  private java.lang.String negativePrefix;  private java.lang.String positiveSuffix;  private java.lang.String negativeSuffix;  private static volatile java.util.regex.Pattern boolPattern;  private static final java.lang.String BOOLEAN_PATTERN;  private java.util.regex.Pattern integerPattern;  private java.lang.String digits;  private java.lang.String non0Digit;  private int SIMPLE_GROUP_INDEX;  private static volatile java.util.regex.Pattern separatorPattern;  private static volatile java.util.regex.Pattern linePattern;  private static final java.lang.String LINE_SEPARATOR_PATTERN;  private static final java.lang.String LINE_PATTERN;  private java.util.regex.Pattern floatPattern;  private java.util.regex.Pattern decimalPattern;  static final boolean $assertionsDisabled;}*/