课堂例子验证

课堂例子验证：

1.// OtherCharMethods.java

// Demonstrate the non-static methods of class

// Character from the java.lang package.

import javax.swing.*;

public class OtherCharMethods {

public static void main( String args[] )

{

Character c1, c2;

c1 = new Character( 'A' );

c2 = new Character( 'a' );

String output =

"c1 = " + c1.charValue() +

" c2 = " + c2.toString() +

" hash code for c1 = " + c1.hashCode() +

" hash code for c2 = " + c2.hashCode();

if ( c1.equals( c2 ) )

output += " c1 and c2 are equal";

else

output += " c1 and c2 are not equal";

JOptionPane.showMessageDialog( null, output,

"Demonstrating Non-Static Character Methods",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

2.// StaticCharMethods.java

// Demonstrates the static character testing methods

// and case conversion methods of class Character

// from the java.lang package.

import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

public class StaticCharMethods extends JFrame {

private char c;

//以下定义几个图形界面组件

private JLabel prompt;

private JTextField input;

private JTextArea outputArea;

public StaticCharMethods()

{

//super代表调用基类JFrame的构造方法，其结果是设置了窗口的标题栏

super( "Static Character Methods" );

//getContentPane是基类提供的方法，它获取窗体中可存放图形控件的空白区域

//所有的可容纳其它图形控件的区域被称为----"容器",它有一个基类,称为Container

Container container = getContentPane();

//设置布局方式为流布局方式:即从左到右地放置控件,一行放不下,就移到下一行

container.setLayout( new FlowLayout() );

prompt =

new JLabel( "Enter a character and press Enter" );

container.add( prompt ); //将控件加入容器中

input = new JTextField( 5 );

//设定文本框对回车键响应

input.addActionListener(

new ActionListener() {

//在下面的函数中定义要干的事

public void actionPerformed( ActionEvent e )

{

String s = e.getActionCommand();

c = s.charAt( 0 );

buildOutput(); //构造输出结果

}

);

container.add( input );

outputArea = new JTextArea( 10, 20 );

container.add( outputArea );

setSize( 300, 250 ); // set the window size

show(); // show the window

}

public void buildOutput()

{

outputArea.setText(

"is defined: " + Character.isDefined( c ) +

" is digit: " + Character.isDigit( c ) + //是否数字

" is Java letter: " +

Character.isJavaIdentifierStart( c ) + //是否可作为标识符的第一个字符

" is Java letter or digit: " +

Character.isJavaIdentifierPart( c ) + //是否可作为标识符的字符

" is letter: " + Character.isLetter( c ) +

" is letter or digit: " +

Character.isLetterOrDigit( c ) +

" is lower case: " + Character.isLowerCase( c ) +

" is upper case: " + Character.isUpperCase( c ) +

" to upper case: " + Character.toUpperCase( c ) +

" to lower case: " + Character.toLowerCase( c ) );

}

//程序入口点

public static void main( String args[] )

{

StaticCharMethods application = new StaticCharMethods();

//只有加上这一句,才能实现单击窗口关闭按钮关闭程序

application.addWindowListener(

new WindowAdapter() {

public void windowClosing( WindowEvent e )

{

System.exit( 0 ); //退出系统

}

);

}

3.// StringBufferAppend.java

// This program demonstrates the append

// methods of the StringBuffer class.

import javax.swing.*;

public class StringBufferAppend {

public static void main( String args[] )

{

Object o = "hello";

String s = "good bye";

char charArray[] = { 'a', 'b', 'c', 'd', 'e', 'f' };

boolean b = true;

char c = 'Z';

int i = 7;

long l = 10000000;

float f = 2.5f;

double d = 33.333;

StringBuffer buf = new StringBuffer();

buf.append( o );

buf.append( " " );

buf.append( s );

buf.append( " " );

buf.append( charArray );

buf.append( " " );

buf.append( charArray, 0, 3 );

buf.append( " " );

buf.append( b );

buf.append( " " );

buf.append( c );

buf.append( " " );

buf.append( i );

buf.append( " " );

buf.append( l );

buf.append( " " );

buf.append( f );

buf.append( " " );

buf.append( d );

JOptionPane.showMessageDialog( null,

"buf = " + buf.toString(),

"Demonstrating StringBuffer append Methods",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

// StringBufferCapLen.java

// This program demonstrates the length and

// capacity methods of the StringBuffer class.

import javax.swing.*;

public class StringBufferCapLen {

public static void main( String args[] )

{

StringBuffer buf =

new StringBuffer( "Hello, how are you?" );

//length:当前字符个数

//capacity:不另外分配内存可以存放的字符个数

String output = "buf = " + buf.toString() +

" length = " + buf.length() +

" capacity = " + buf.capacity();

//ensureCapacity:保证StringBuffer的最小容量

buf.ensureCapacity( 75 );

output += " New capacity = " + buf.capacity();

//setLength:增大或减小StringBuffer的长度

buf.setLength( 10 );

output += " New length = " + buf.length() +

" buf = " + buf.toString();

JOptionPane.showMessageDialog( null, output,

"StringBuffer length and capacity Methods",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

//StringBufferChars.java

// The charAt, setCharAt, getChars, and reverse methods

// of class StringBuffer.

import javax.swing.*;

public class StringBufferChars {

public static void main( String args[] )

{

StringBuffer buf = new StringBuffer( "hello there" );

String output = "buf = " + buf.toString() +

" Character at 0: " + buf.charAt( 0 ) +

" Character at 4: " + buf.charAt( 4 );

char charArray[] = new char[ buf.length() ];

buf.getChars( 0, buf.length(), charArray, 0 );

//(起始下标,长度,字符数组名,起始下标)

output += " The characters are: ";

for ( int i = 0; i < charArray.length; ++i )

output += charArray[ i ];

buf.setCharAt( 0, 'H' );

buf.setCharAt( 6, 'T' );

output += " buf = " + buf.toString();

//reverse:倒转字串

buf.reverse();

output += " buf = " + buf.toString();

JOptionPane.showMessageDialog( null, output,

"Demonstrating StringBuffer Character Methods",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

// StringBufferConstructors.java

// This program demonstrates the StringBuffer constructors.

import javax.swing.*;

public class StringBufferConstructors {

public static void main( String args[] )

{

StringBuffer buf1, buf2, buf3;

buf1 = new StringBuffer();

buf2 = new StringBuffer( 10 );

buf3 = new StringBuffer( "hello" );

String output =

"buf1 = " + """ + buf1.toString() + """ +

" buf2 = " + """ + buf2.toString() + """ +

" buf3 = " + """ + buf3.toString() + """;

JOptionPane.showMessageDialog( null, output,

"Demonstrating StringBuffer Class Constructors",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

// StringBufferInsert.java

// This program demonstrates the insert and delete

// methods of class StringBuffer.

import javax.swing.*;

public class StringBufferInsert {

public static void main( String args[] )

{

Object o = "hello";

String s = "good bye";

char charArray[] = { 'a', 'b', 'c', 'd', 'e', 'f' };

boolean b = true;

char c = 'K';

int i = 7;

long l = 10000000;

float f = 2.5f;

double d = 33.333;

StringBuffer buf = new StringBuffer();

buf.insert( 0, o );

buf.insert( 0, " " );

buf.insert( 0, s );

buf.insert( 0, " " );

buf.insert( 0, charArray );

buf.insert( 0, " " );

buf.insert( 0, b );

buf.insert( 0, " " );

buf.insert( 0, c );

buf.insert( 0, " " );

buf.insert( 0, i );

buf.insert( 0, " " );

buf.insert( 0, l );

buf.insert( 0, " " );

buf.insert( 0, f );

buf.insert( 0, " " );

buf.insert( 0, d );

String output = "buf after inserts: " + buf.toString();

buf.deleteCharAt( 10 ); // delete 5 in 2.5

buf.delete( 2, 6 ); // delete .333 in 33.333

output += " buf after deletes: " + buf.toString();

JOptionPane.showMessageDialog( null, output,

"Demonstrating StringBufferer Inserts and Deletes",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

// StringCompare

// This program demonstrates the methods equals,

// equalsIgnoreCase, compareTo, and regionMatches

// of the String class.

import javax.swing.JOptionPane;

public class StringCompare {

public static void main( String args[] )

{

String s1, s2, s3, s4, output;

s1 = new String( "hello" );

s2 = new String( "good bye" );

s3 = new String( "Happy Birthday" );

s4 = new String( "happy birthday" );

output = "s1 = " + s1 + " s2 = " + s2 +

" s3 = " + s3 + " s4 = " + s4 + " ";

//test for equality

//equals用于比较两对象的内容是否相等.

//自定义对象时需要重载此方法

if ( s1.equals( "hello" ) )

output += "s1 equals "hello" ";

else

output += "s1 does not equal "hello" ";

// test for equality with ==

//比对引用.只有两个引用指向同一个对象,则结果为true

if ( s1 == "hello" )

output += "s1 == "hello" ";

else

output += "s1 does not == "hello" ";

// test for equality--ignore case

if ( s3.equalsIgnoreCase( s4 ) )

output += "s3 equals s4 ";

else

output += "s3 does not equal s4 ";

// test compareTo

//使用字典法进行比较,返回0表两字串相等,小于返回负值,大于返回正值

output +=

" s1.compareTo( s2 ) is " + s1.compareTo( s2 ) +

" s2.compareTo( s1 ) is " + s2.compareTo( s1 ) +

" s1.compareTo( s1 ) is " + s1.compareTo( s1 ) +

" s3.compareTo( s4 ) is " + s3.compareTo( s4 ) +

" s4.compareTo( s3 ) is " + s4.compareTo( s3 ) +

" ";

// test regionMatches (case sensitive)

//比较两字串中的某一部分是否相等

//参数含义如下:

//1.调用这个方法的字串中的起始下标

//2.要比较的字串

//3.要比较的字串的起始下标

//4.要比较的字串比较的字符长度

if ( s3.regionMatches( 0, s4, 0, 5 ) )

output += "First 5 characters of s3 and s4 match ";

else

output +=

"First 5 characters of s3 and s4 do not match ";

// test regionMatches (ignore case)

if ( s3.regionMatches( true, 0, s4, 0, 5 ) )

output += "First 5 characters of s3 and s4 match";

else

output +=

"First 5 characters of s3 and s4 do not match";

JOptionPane.showMessageDialog( null, output,

"Demonstrating String Class Constructors",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

/**************************************************************************

* *

* DISCLAIMER: The authors and publisher of this book have used their *

* best efforts in preparing the book. These efforts include the *

* development, research, and testing of the theories and programs *

* to determine their effectiveness. The authors and publisher make *

* no warranty of any kind, expressed or implied, with regard to these *

* programs or to the documentation contained in these books. The authors *

* and publisher shall not be liable in any event for incidental or *

* consequential damages in connection with, or arising out of, the *

* furnishing, performance, or use of these programs. *

*************************************************************************/

// StringConcat.java

// This program demonstrates the String class concat method.

// Note that the concat method returns a new String object. It

// does not modify the object that invoked the concat method.

import javax.swing.*;

public class StringConcat {

public static void main( String args[] )

{

String s1 = new String( "Happy " ),

s2 = new String( "Birthday" ),

output;

output = "s1 = " + s1 +

" s2 = " + s2;

output += " Result of s1.concat( s2 ) = " +

s1.concat( s2 );

output += " s1 after concatenation = " + s1;

JOptionPane.showMessageDialog( null, output,

"Demonstrating String Method concat",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

10.

// StringConstructors.java

// This program demonstrates the String class constructors.

import javax.swing.*;

public class StringConstructors {

public static void main( String args[] )

{

char charArray[] = { 'b', 'i', 'r', 't', 'h', ' ',

'd', 'a', 'y' };

byte byteArray[] = { (byte) 'n', (byte) 'e', (byte) 'w',

(byte) ' ', (byte) 'y', (byte) 'e',

(byte) 'a', (byte) 'r' };

StringBuffer buffer;

String s, s1, s2, s3, s4, s5, s6, s7, output;

s = new String( "hello" );

buffer = //分配缓冲区

new StringBuffer( "Welcome to Java Programming!" );

// use the String constructors

s1 = new String(); //缺省构造函数

s2 = new String( s ); //拷贝构造函数

s3 = new String( charArray ); //以字符数组初始化字串

s4 = new String( charArray, 6, 3 ); //从字符数组第6个元素起取3个字符

s5 = new String( byteArray, 4, 4 ); //从字节数组第4个元素起取4个字节

s6 = new String( byteArray );

s7 = new String( buffer ); //从缓冲区中提取字符创建字串,注意,是复制

output = "s1 = " + s1 +

" s2 = " + s2 +

" s3 = " + s3 +

" s4 = " + s4 +

" s5 = " + s5 +

" s6 = " + s6 +

" s7 = " + s7;

JOptionPane.showMessageDialog( null, output,

"Demonstrating String Class Constructors",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

11.

public class StringEquals {

/**

* @param args the command line arguments

public static void main(String[] args) {

String s1=new String("Hello");

String s2=new String("Hello");

System.out.println(s1==s2);

System.out.println(s1.equals(s2));

String s3="Hello";

String s4="Hello";

System.out.println(s3==s4);

System.out.println(s3.equals(s4));

}

12.

// StringHashCode.java

// This program demonstrates the method

// hashCode of the String class.

import javax.swing.*;

public class StringHashCode {

public static void main( String args[] )

{

String s1 = "hello",

s2 = "Hello";

String output =

"The hash code for "" + s1 + "" is " +

s1.hashCode() +

" The hash code for "" + s2 + "" is " +

s2.hashCode();

JOptionPane.showMessageDialog( null, output,

"Demonstrating String Method hashCode",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

13.

//StringIndexMethods.java

// This program demonstrates the String

// class index methods.

import javax.swing.*;

public class StringIndexMethods {

public static void main( String args[] )

{

String letters = "abcdefghijklmabcdefghijklm";

String output;

// test indexOf to locate a character in a string

output = "'c' is located at index " +

letters.indexOf( 'c' );

output += " 'a' is located at index " +

letters.indexOf( 'a', 1 ); //第2个参数是开始查找的起始下标

output += " '$' is located at index " +

letters.indexOf( '$' );

// test lastIndexOf to find a character in a string

output += " Last 'c' is located at index " +

letters.lastIndexOf( 'c' );

output += " Last 'a' is located at index " +

letters.lastIndexOf( 'a', 25 );

output += " Last '$' is located at index " +

letters.lastIndexOf( '$' );

// test indexOf to locate a substring in a string

output += " "def" is located at index " +

letters.indexOf( "def" );

output += " "def" is located at index " +

letters.indexOf( "def", 7 );

output += " "hello" is located at index " +

letters.indexOf( "hello" );

// test lastIndexOf to find a substring in a string

output += " Last "def" is located at index " +

letters.lastIndexOf( "def" );

output += " Last "def" is located at index " +

letters.lastIndexOf( "def", 25 );

output += " Last "hello" is located at index " +

letters.lastIndexOf( "hello" );

JOptionPane.showMessageDialog( null, output,

"Demonstrating String Class "index" Methods",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

14.

//StringMisc.java

// This program demonstrates the length, charAt and getChars

// methods of the String class.

// Note: Method getChars requires a starting point

// and ending point in the String. The starting point is the

// actual subscript from which copying starts. The ending point

// is one past the subscript at which the copying ends.

import javax.swing.*;

public class StringMisc {

public static void main( String args[] )

{

String s1, output;

char charArray[];

s1 = new String( "hello there" );

charArray = new char[ 5 ];

// output the string

output = "s1: " + s1;

// test the length method

output += " Length of s1: " + s1.length();

// loop through the characters in s1 and display reversed

output += " The string reversed is: ";

for ( int i = s1.length() - 1; i >= 0; i-- )

output += s1.charAt( i ) + " ";

// copy characters from string into char array

//四个参数的含义

//1.被拷贝字符在字串中的起始位置

//2.被拷贝的最后一个字符在字串中的下标再加1

//3.目标字符数组

//4.拷贝的字符放在字符数组中的起始下标

s1.getChars( 0, 5, charArray, 0 );

output += " The character array is: ";

for ( int i = 0; i < charArray.length;i++ )

output += charArray[ i ];

JOptionPane.showMessageDialog( null, output,

"Demonstrating String Class Constructors",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

15.

public class StringPool {

public static void main(String args[])

{

String s0="Hello";

String s1="Hello";

String s2="He"+"llo";

System.out.println(s0==s1);//true

System.out.println(s0==s2);//true

System.out.println(new String("Hello")==new String("Hello"));//false

}

16.

// StringStartEnd.java

// This program demonstrates the methods startsWith and

// endsWith of the String class.

import javax.swing.*;

public class StringStartEnd {

public static void main( String args[] )

{

String strings[] = { "started", "starting",

"ended", "ending" };

String output = "";

// Test method startsWith

for ( int i = 0; i < strings.length; i++ )

if ( strings[ i ].startsWith( "st" ) )

output += """ + strings[ i ] +

"" starts with "st" ";

output += " ";

// Test method startsWith starting from position

// 2 of the string

for ( int i = 0; i < strings.length; i++ )

if ( strings[ i ].startsWith( "art", 2 ) )

output +=

""" + strings[ i ] +

"" starts with "art" at position 2 ";

output += " ";

// Test method endsWith

for ( int i = 0; i < strings.length; i++ )

if ( strings[ i ].endsWith( "ed" ) )

output += """ + strings[ i ] +

"" ends with "ed" ";

JOptionPane.showMessageDialog( null, output,

"Demonstrating String Class Comparisons",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

17.

// StringValueOf.java

// This program demonstrates the String class valueOf methods.

import javax.swing.*;

public class StringValueOf {

public static void main( String args[] )

{

char charArray[] = { 'a', 'b', 'c', 'd', 'e', 'f' };

boolean b = true;

char c = 'Z';

int i = 7;

long l = 10000000;

float f = 2.5f;

double d = 33.333;

Object o = "hello"; // Assign to an Object reference

String output;

output = "char array = " + String.valueOf( charArray ) +

" part of char array = " +

String.valueOf( charArray, 3, 3 ) +

" boolean = " + String.valueOf( b ) +

" char = " + String.valueOf( c ) +

" int = " + String.valueOf( i ) +

" long = " + String.valueOf( l ) +

" float = " + String.valueOf( f ) +

" double = " + String.valueOf( d ) +

" Object = " + String.valueOf( o );

JOptionPane.showMessageDialog( null, output,

"Demonstrating String Class valueOf Methods",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

18.

// SubString.java

// This program demonstrates the

// String class substring methods.

import javax.swing.*;

public class SubString {

public static void main( String args[] )

{

String letters = "abcdefghijklmabcdefghijklm";

String output;

// test substring methods

output = "Substring from index 20 to end is " +

""" + letters.substring( 20 ) + "" ";

output += "Substring from index 0 up to 6 is " +

""" + letters.substring( 0, 6 ) + """;

//(起始下标,要拷贝子串的最后下标加1但不包括该下标)

JOptionPane.showMessageDialog( null, output,

"Demonstrating String Class Substring Methods",

JOptionPane.INFORMATION_MESSAGE );

System.exit( 0 );

}

19.

public class Test {

/**

* @param args

public static void main(String[] args) {

String aString="abc";

String bString="abc";

bString=new String("abc");

System.out.println(aString==bString);

bString += "def";

System.out.println(bString);

}

20.

// TokenTest.java

// Testing the StringTokenizer class of the java.util package

import javax.swing.*;

import java.util.*;

import java.awt.*;

import java.awt.event.*;

public class TokenTest extends JFrame {

private JLabel prompt;

private JTextField input;

private JTextArea output;

public TokenTest()

{

super( "Testing Class StringTokenizer" );

Container c = getContentPane();

c.setLayout( new FlowLayout() );

prompt =

new JLabel( "Enter a sentence and press Enter" );

c.add( prompt );

input = new JTextField( 20 );

input.addActionListener(

new ActionListener() {

public void actionPerformed( ActionEvent e )

{

//获取用户输入的字串

String stringToTokenize = e.getActionCommand();

StringTokenizer tokens =

new StringTokenizer( stringToTokenize );

//使用缺省构造函数,定界符为:空格,换行符,TAB

output.setText( "Number of elements: " +

tokens.countTokens() +

" The tokens are: " );

while ( tokens.hasMoreTokens() )

output.append( tokens.nextToken() + " " );

}

);

c.add( input );

output = new JTextArea( 10, 20 );

output.setEditable( false );

c.add( new JScrollPane( output ) );

setSize( 275, 260 ); // set the window size

show(); // show the window

}

public static void main( String args[] )

{

TokenTest app = new TokenTest();

app.addWindowListener(

new WindowAdapter() {

public void windowClosing( WindowEvent e )

{

System.exit( 0 );

}

);

}