1.switch
package com.chap1.switch_string;
/**
*
* Switch_String
*
* @author ajan
* @since 1.7.0_51
* @version 1.0.0 2014 12 22
*
*/
public class Title
{
public String generate(String name, String gender)
{
String title = "";
// case
switch (gender)
{
case " ":
title = name + " ";
break;
case " ":
title = name + " ";
break;
// case null,
// case null;
// break;
default:
title = name;
}
return title;
}
public static void main(String[] args)
{
Title title = new Title();
System.out.println(title.generate("kobe", " "));
// null，
// System.out.println(title.generate("kobe", null));
}
}
package com.chap1.switch_string;
/**
*
* case ,Java Unicode .-> Java Java ->
* Unicode -> case ， ，
*
* <pre>
*
* 1. 。Java , ,
* 2. case ， ， ，
* 3.
* 1.switch case-> if
* 2.switch case, default-> if/else
* 3. case-> Java7 case-> hash
* 4. :Title.jad
* jad Title.class
* 5.Title.jd jd-gui .
* 6. ， :switch(s.hashCode())
* 7. jad ，+ StringBuilder.append ->
* 8. swich_string-> , ， -> case . ， .
* </pre>
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 22
*
*/
public class TitleDuplicate
{
public String generate(String name, String gender)
{
String title = "";
// :Duplicate case， case ,
// \u7537 " " Unicode
switch (gender)
{
// case " ":
// title = name + " ";
// break;
case "\u7537":
break;
default:
}
return title;
}
}
// Decompiled by Jad v1.5.8g. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://www.kpdus.com/jad.html
// Decompiler options: packimports(3)
// Source File Name: Title.java
package com.chap1.switch_string;
import java.io.PrintStream;
public class Title
{
public Title()
{
}
public String generate(String name, String gender)
{
String title;
label0:
{
title = "";
String s;
switch((s = gender).hashCode())
{
default:
break;
case 22899:
if(!s.equals("\u5973"))
break;
title = (new StringBuilder(String.valueOf(name))).append(" \u5973\u58EB").toString();
break label0;
case 30007:
if(s.equals("\u7537"))
{
title = (new StringBuilder(String.valueOf(name))).append(" \u5148\u751F").toString();
break label0;
}
break;
}
title = name;
}
return title;
}
public static void main(String args[])
{
Title title = new Title();
System.out.println(title.generate("kobe", "\u7537"));
}
}
package com.chap1.switch_string;
import java.io.PrintStream;
public class Title
{
public String generate(String name, String gender)
{
String title = "";
String str1;
switch ((str1 = gender).hashCode())
{
case 22899:
if (str1.equals(" ")) {
break;
}
case 30007:
if ((goto 108) && (str1.equals(" ")))
{
title = name + " ";
return title;
title = name + " ";
}
break;
}
title = name;
return title;
}
public static void main(String[] args)
{
Title title = new Title();
System.out.println(title.generate("kobe", " "));
}
}
2.
package com.chap1.binary_literal;
/**
*
*
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 22
*
*/
public class BinaryIntegralLiteral
{
//
public void displayBinaryLiteral()
{
// 0b/0B
System.out.println(0b1001);
System.out.println(0B1111);
System.out.println(0b01111111);
}
//
public void displayOctalLiteral()
{
// 0 8
// 1 * 8 + 7 = 15
System.out.println(017);
// 1 * 8 + 2 * 8 + 7 = 87
System.out.println(0127);
}
//
public void displayHexLiteral()
{
// 0x/0X 16
// a,b,c,d,e,f 10,11,12,13,14,15
// 15
System.out.println(0xf);
// 1 * 16 + 15 = 31
System.out.println(0X1f);
// 2 * 16 + 10 = 42
System.out.println(0x2a);
}
public static void main(String[] args)
{
BinaryIntegralLiteral bil = new BinaryIntegralLiteral();
bil.displayBinaryLiteral();
bil.displayOctalLiteral();
bil.displayHexLiteral();
}
}
package com.chap1.binary_literal;
/**
*
* -> -> -> ->
* -> ->
* -> -> ， _100 ，
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 22
*
*/
public class Underscore
{
public void display()
{
System.out.println(1_500_000);
double value1 = 5_6.3_4;
//
int value2 = 89_3__1;
System.out.println(value1);
System.out.println(value2);
}
public static void main(String[] args)
{
Underscore underscore = new Underscore();
underscore.display();
}
}
3.
package com.chap1.exception_optimize;
/**
*
* Java7 catch ， ， “|” , catch
* ->#throwManyExceptions
* :1.catch ， ， 。
* ->#throwSubExceptions
* 2. catch ， ( “e” )。
* ->#throwIncludeRuntimeException
* 3. ， 。
* ->landon:
* ， ， ， #throwIncludeRuntimeException catch
* NullPointerException ， ( jdk7 )
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 24
*
*/
public class CatchManyExceptions
{
//
public void throwManyExceptions() throws ExceptionA, ExceptionB, ExceptionC
{
}
// :D C
public void throwSubExceptions() throws ExceptionC, ExceptionD
{
}
// RunTimeException
public void throwIncludeRuntimeException() throws NullPointerException,
RuntimeException
{
}
// ，D,E C
public void throw2SubExceptions() throws ExceptionD, ExceptionE
{
}
public static void main(String[] args)
{
CatchManyExceptions catchManyExceptions = new CatchManyExceptions();
try
{
// Ctrl + 1,Surround with try/multi-catch
catchManyExceptions.throwManyExceptions();
} catch (ExceptionA | ExceptionB e)
{
System.err.println("catch Exception A | B");
} catch (ExceptionC e)
{
System.err.println("catch Exception C");
}
// :The exception ExceptionD is already caught by the
// alternative ExceptionC
// try
// {
// catchManyExceptions.throwSubExceptions();
// } catch (ExceptionD | ExceptionC e)
// {
// }
// : The exception ExceptionD is already caught by the
// alternative ExceptionC
// try
// {
// catchManyExceptions.throwSubExceptions();
// } catch ExceptionC | ExceptionD e)
// {
// }
// jdk1.7
try
{
catchManyExceptions.throwSubExceptions();
} catch (ExceptionD e)
{
e.printStackTrace();
} catch (ExceptionC e)
{
e.printStackTrace();
}
// :The exception NullPointerException is already caught by the
// alternative RuntimeException
// try
// {
// catchManyExceptions.throwIncludeRuntimeException();
// } catch (RuntimeException | NullPointerException e)
// {
// }
// The exception NullPointerException is already caught by the
// alternative RuntimeException
// try
// {
// catchManyExceptions.throwIncludeRuntimeException();
// } catch (NullPointerException | RuntimeException e)
// {
// }
try
{
catchManyExceptions.throwIncludeRuntimeException();
} catch (NullPointerException e)
{
} catch (RuntimeException e)
{
}
// D E C , “e”
try
{
catchManyExceptions.throw2SubExceptions();
} catch (ExceptionD | ExceptionE e)
{
//
e.exception_c();
}
}
}
class ExceptionA extends Exception
{
}
class ExceptionB extends Exception
{
}
class ExceptionC extends Exception
{
public void exception_c()
{
System.err.println("i'm exception c");
}
}
// D C
class ExceptionD extends ExceptionC
{
}
// E C;
class ExceptionE extends ExceptionC
{
}
package com.chap1.exception_optimize;
import java.io.FileInputStream;
import java.io.IOException;
/**
*
*
* <pre>
* 1.
* 2. ， ，
* 3. ， 。 。
* 4.Throwable ， , cause
* public Throwable(Throwable cause)
* 5. ， 。
*
* </pre>
*
* <output>
* Exception in thread "main" com.chap1.exception_optimize.DataAccessException: java.io.FileNotFoundException: data.txt ( 。)
at com.chap1.exception_optimize.DataAccessGateway.load(DataAccessGateway.java:34)
at com.chap1.exception_optimize.DataAccessGateway.main(DataAccessGateway.java:41)
Caused by: java.io.FileNotFoundException: data.txt ( 。)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(Unknown Source)
at java.io.FileInputStream.<init>(Unknown Source)
at com.chap1.exception_optimize.DataAccessGateway.load(DataAccessGateway.java:30)
1 more
* </output>
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 23
*
*/
public class DataAccessGateway
{
public void load() throws DataAccessException
{
try
{
FileInputStream input = new FileInputStream("data.txt");
} catch (IOException e)
{
// DataAccessException， IOException ,
throw new DataAccessException(e);
}
}
public static void main(String[] args)
{
DataAccessGateway gateway = new DataAccessGateway();
gateway.load();
}
}
//
class DataAccessException extends RuntimeException
{
public DataAccessException(Throwable cause)
{
super(cause);
}
}
package com.chap1.exception_optimize;
/**
*
* “ ”, catch NumberFormatException( )； finally ArithmeticException( )
* ： try ， ，finally
*
* <output>
* Exception in thread "main" com.chap1.exception_optimize.BaseException: java.lang.ArithmeticException: / by zero
at com.chap1.exception_optimize.DisappearException.show(DisappearException.java:30)
at com.chap1.exception_optimize.DisappearException.main(DisappearException.java:38)
Caused by: java.lang.ArithmeticException: / by zero
at com.chap1.exception_optimize.DisappearException.show(DisappearException.java:27)
1 more
* </output>
*
* ， finally ArithmeticException , try “ ” . ， ，
* finally （ ）， ，
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 23
*
*/
public class DisappearException
{
public void show() throws BaseException
{
try
{
Integer.parseInt("hello");
} catch (NumberFormatException e)
{
throw new BaseException(e);
} finally
{
try
{
int result = 2 / 0;
} catch (ArithmeticException e)
{
throw new BaseException(e);
}
}
}
public static void main(String[] args)
{
DisappearException disappearException = new DisappearException();
disappearException.show();
}
}
class BaseException extends RuntimeException
{
public BaseException(Throwable cause)
{
super(cause);
}
}
package com.chap1.exception_optimize;
/**
*
* Throwable#void addSuppressed(Throwable exception) ' '
* ， "Suppressed"
*
* <output>
* Exception in thread "main" com.chap1.exception_optimize.BaseException: java.lang.NumberFormatException: For input string: "hello"
at com.chap1.exception_optimize.DisappearExceptionResolve.show(DisappearExceptionResolve.java:43)
at com.chap1.exception_optimize.DisappearExceptionResolve.main(DisappearExceptionResolve.java:51)
Caused by: java.lang.NumberFormatException: For input string: "hello"
at java.lang.NumberFormatException.forInputString(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at com.chap1.exception_optimize.DisappearExceptionResolve.show(DisappearExceptionResolve.java:21)
1 more
Suppressed: java.lang.ArithmeticException: / by zero
at com.chap1.exception_optimize.DisappearExceptionResolve.show(DisappearExceptionResolve.java:29)
1 more
* </output>
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 23
*
*/
public class DisappearExceptionResolve
{
public void show() throws BaseException
{
Throwable throwable = null;
try
{
Integer.parseInt("hello");
} catch (NumberFormatException e)
{
throwable = e;
} finally
{
try
{
int result = 2 / 0;
} catch (ArithmeticException e)
{
if (throwable != null)
{
throwable.addSuppressed(e);
} else
{
throwable = e;
}
}
if (throwable != null)
{
throw new BaseException(throwable);
}
}
}
public static void main(String[] args)
{
DisappearExceptionResolve resolve = new DisappearExceptionResolve();
resolve.show();
}
}
package com.chap1.exception_optimize;
import java.math.BigDecimal;
/**
*
*
*
* <pre>
* 1.native2ascii， ， ->\u4f59\u989d\u4e0d\u8db3
* 2. message_zh_cn.properties
* </pre>
*
* <output>
* Exception in thread "main" com.chap1.exception_optimize.InsufficientBalanceException: ：8.09：10.32：2.23
at com.chap1.exception_optimize.InsufficientBalanceException.main(InsufficientBalanceException.java:47)
* </output>
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 23
*
*/
public class InsufficientBalanceException extends LocalizedException
{
//
private BigDecimal requested;
//
private BigDecimal balance;
//
private BigDecimal shortage;
public InsufficientBalanceException(BigDecimal requested,BigDecimal balance)
{
super("INSUFFICIENT_BALANCE_EXCEPTION");
this.requested = requested;
this.balance = balance;
this.shortage = requested.subtract(balance);
}
@Override
public String getLocalizedMessage()
{
return format(balance,requested,shortage);
}
public static void main(String[] args) throws Exception
{
throw new InsufficientBalanceException(new BigDecimal("10.32") , new BigDecimal("8.09"));
}
}
package com.chap1.exception_optimize;
import java.text.MessageFormat;
import java.util.ResourceBundle;
/**
*
* , ResourceBundle
*
* <pre>
* 1. （properties）， .properties （ ）， （ ）， properties 。
* ， ， properties ： ： _ _ .properties，
* 2. ， ： .properties
* 3. ：msg_en_US.properties,msg_zh_CN.properties,msg.properties
* 4. ISO-8859-1 ->native2ascii
* 5.MessageFormat:
* </pre>
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 23
*
*/
public abstract class LocalizedException extends Exception
{
private String messageKey;
protected ResourceBundle resourceBundle;
public LocalizedException(String msgKey)
{
messageKey = msgKey;
initResouceBundle();
}
public abstract String getLocalizedMessage();
//
@Override
public String getMessage()
{
return getLocalizedMessage();
}
private void initResouceBundle()
{
resourceBundle = ResourceBundle.getBundle("message_zh_CN");
}
protected String format(Object args)
{
String message = resourceBundle.getString(messageKey);
return MessageFormat.format(message, args);
}
}
package com.chap1.exception_optimize;
/**
*
* Java7 ， catch catch ，
* try ， catch
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 28
*
*/
public class PreciseThrowUse
{
public void testThrow() throws ExceptionA
{
try
{
throw new ExceptionASub2();
} catch (ExceptionA e)
{
// : ExceptionASub2, catchExceptionASub1
// Java6 :1. try catch ExceptionA, catch ( )
// ExceptionA ExceptionASub1 .
// try
// {
// throw e;
// }
// catch(ExceptionASub1 e2)
// {
//
// }
// , e ExceptionASub2
// try
// {
// throw e;
// } catch (ExceptionASub2 e2)
// {
//
// }
// , e ExceptionA
try
{
throw e;
} catch (ExceptionA e3)
{
}
}
}
}
// ExceptionA 1
class ExceptionASub1 extends ExceptionA
{
}
// ExceptionA 2
class ExceptionASub2 extends ExceptionA
{
}
package com.chap1.exception_optimize;
import java.io.FileInputStream;
import java.io.IOException;
/**
*
* " "， ： ， Java7 Throwable addSuppressed .
* ，
* ， addSuppressed 。
* ， getSuppressed 。 ， 。
* Throwable 1.7
*
* <pre>
* * @serial
* @since 1.7
*
* private List<Throwable> suppressedExceptions = SUPPRESSED_SENTINEL;
* </pre>
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 23
*
*/
public class ReadFileAddSuppressedException
{
// finally addSuppressed try
public void read(String fileName) throws BaseException
{
FileInputStream input = null;
IOException ioException = null;
try
{
input = new FileInputStream(fileName);
} catch (IOException e)
{
ioException = e;
} finally
{
if (input != null)
{
try
{
input.close();
} catch (IOException e)
{
if (ioException != null)
{
// “suppressedExceptions”
ioException.addSuppressed(e);
} else
{
ioException = e;
}
}
}
if (ioException != null)
{
throw new BaseException(ioException);
}
}
}
}
package com.chap1.exception_optimize;
import java.io.FileInputStream;
import java.io.IOException;
/**
*
* " "， ：
* 1. try ， finally ， try
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 23
*
*/
public class ReadFileIgnoreFinallyException
{
public void read(String fileName) throws BaseException
{
FileInputStream input = null;
IOException ioException = null;
try
{
input = new FileInputStream(fileName);
}
catch(IOException e)
{
ioException = e;
}
finally
{
if(input != null)
{
try
{
input.close();
}
catch(IOException e)
{
if(ioException == null)
{
ioException = e;
}
}
}
if(ioException != null)
{
throw new BaseException(ioException);
}
}
}
}
INSUFFICIENT_BALANCE_EXCEPTION = insufficient balance:{0}:{1}:{2}
INSUFFICIENT_BALANCE_EXCEPTION = \u4f59\u989d\u4e0d\u8db3\uFF1A{0}\uFF1A{1}\uFF1A{2}
4.try-with-resources
package com.chap1.try_resources;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
/**
*
* 1.1.7 try , try-with-resources
* 2. : ， ( ， ， ， )-> ， ，
* 3.1.7 try-catch-finall finally ， ，
* 4.1.7 try ， ，
* 5. , try ， ， try ； ， try ，
* Throwable#addSuppressed
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 28
*
*/
public class ResourceBasicUse
{
public String readFile(String path) throws IOException
{
// try()
// finally , 。 finally ，
try (BufferedReader reader = new BufferedReader(new FileReader(path)))
{
StringBuilder builder = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null)
{
builder.append(line);
//
builder.append(String.format("%n"));
}
return builder.toString();
}
}
public static void main(String[] args) throws Exception
{
ResourceBasicUse basicUse = new ResourceBasicUse();
basicUse.readFile("tmp.txt");
}
}
package com.chap1.try_resources;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
/**
*
* try-with-resources
* 1. , ； try
* 2.try-with-resources catch finally 。 catch try
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 28
*
*/
public class MultiResourceUse
{
//
public void copyFile(String fromPath, String toPath) throws IOException
{
// , input output
try (InputStream input = new FileInputStream(fromPath);
OutputStream output = new FileOutputStream(toPath))
{
byte[] bytes = new byte[8192];
int len = -1;
while ((len = input.read(bytes)) != -1)
{
output.write(bytes, 0, len);
}
}
// catch
catch (Exception e)
{
e.printStackTrace();
}
// finally
finally
{
System.out.println("copy file.finally");
}
}
public static void main(String[] args) throws Exception
{
MultiResourceUse mru = new MultiResourceUse();
mru.copyFile("source.txt", "dest.txt");
}
}
package com.chap1.try_resources;
/**
* 1. try ： Java AutoCloseable . . ，
* close . 2.Java 。-> IO .
* :java.io.Closeable extends AutoCloseable ;java.sql.Connection extends
* Wrapper, AutoCloseable
* 3. try , AutoCloseable close .
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 28
*
*/
public class CustomResource implements AutoCloseable
{
@Override
public void close() throws Exception
{
System.out.println(" ");
}
public void useCustomResource() throws Exception
{
try (CustomResource resource = new CustomResource())
{
System.out.println(" ");
}
}
public static void main(String[] args) throws Exception
{
// Resource leak: 'cr' is never closed
CustomResource cr = new CustomResource();
//
//
// :close
cr.useCustomResource();
}
}
5.
package com.chap1.varargs_optimize;
import java.util.ArrayList;
/**
*
* 1.Java7 ， : , useVarargs
* ，Java7
* :@SafeVarargs， , 。
* : static final
* (landon:why: ? )， . useVarargs3
*
*
* <pre>
* @Documented
* @Retention(RetentionPolicy.RUNTIME)
* @Target({ ElementType.CONSTRUCTOR, ElementType.METHOD })
* public @interface SafeVarargs
* {
* }
* </pre>
*
* @author landon
* @since 1.7.0_51
* @version 1.0.0 2014 4 28
*
*/
public class VarargsOptimize
{
// ， List<String> ， .
// , .
// Arrays.asList/Collections.addAll
public static <T> T useVarargs(T args)
{
return args.length > 0 ? args[0] : null;
}
//
@SafeVarargs
public static <T> T useVarargs2(T args)
{
return args.length > 0 ? args[0] : null;
}
// :@SafeVarargs annotation cannot be applied to non-final instance
// method useVarargs3, final
// @SafeVarargs
// public <T> T useVarargs3(T args)
// {
// return args.length > 0 ? args[0] : null;
// }
// ， final : ： ， .
@SafeVarargs
public final <T> T useVarargs4(T args)
{
return args.length > 0 ? args[0] : null;
}
public static void main(String[] args)
{
// :Type safety: A generic array of ArrayList<String> is created for a
// varargs parameter
useVarargs(new ArrayList<String>());
// , @SafeVarargs
useVarargs2(new ArrayList<String>());
}
}