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() +
"\nc2 = " + c2.toString() +
"\n\nhash code for c1 = " + c1.hashCode() +
"\nhash code for c2 = " + c2.hashCode();
if ( c1.equals( c2 ) )
output += "\n\nc1 and c2 are equal";
else
output += "\n\nc1 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 ) +
"\nis digit: " + Character.isDigit( c ) + //是否数字
"\nis Java letter: " +
Character.isJavaIdentifierStart( c ) + //是否可作为标识符的第一个字符
"\nis Java letter or digit: " +
Character.isJavaIdentifierPart( c ) + //是否可作为标识符的字符
"\nis letter: " + Character.isLetter( c ) +
"\nis letter or digit: " +
Character.isLetterOrDigit( c ) +
"\nis lower case: " + Character.isLowerCase( c ) +
"\nis upper case: " + Character.isUpperCase( c ) +
"\nto upper case: " + Character.toUpperCase( c ) +
"\nto 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 );
}
}
4.
// 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() +
"\nlength = " + buf.length() +
"\ncapacity = " + buf.capacity();
//ensureCapacity:保证StringBuffer的最小容量
buf.ensureCapacity( 75 );
output += "\n\nNew capacity = " + buf.capacity();
//setLength:增大或减小StringBuffer的长度
buf.setLength( 10 );
output += "\n\nNew length = " + buf.length() +
"\nbuf = " + buf.toString();
JOptionPane.showMessageDialog( null, output,
"StringBuffer length and capacity Methods",
JOptionPane.INFORMATION_MESSAGE );
System.exit( 0 );
}
}
5.
//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() +
"\nCharacter at 0: " + buf.charAt( 0 ) +
"\nCharacter 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 += "\n\nThe characters are: ";
for ( int i = 0; i < charArray.length; ++i )
output += charArray[ i ];
buf.setCharAt( 0, 'H' );
buf.setCharAt( 6, 'T' );
output += "\n\nbuf = " + buf.toString();
//reverse:倒转字串
buf.reverse();
output += "\n\nbuf = " + buf.toString();
JOptionPane.showMessageDialog( null, output,
"Demonstrating StringBuffer Character Methods",
JOptionPane.INFORMATION_MESSAGE );
System.exit( 0 );
}
}
6.
// 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() + "\"" +
"\nbuf2 = " + "\"" + buf2.toString() + "\"" +
"\nbuf3 = " + "\"" + buf3.toString() + "\"";
JOptionPane.showMessageDialog( null, output,
"Demonstrating StringBuffer Class Constructors",
JOptionPane.INFORMATION_MESSAGE );
System.exit( 0 );
}
}
7.
// 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:\n" + buf.toString();
buf.deleteCharAt( 10 ); // delete 5 in 2.5
buf.delete( 2, 6 ); // delete .333 in 33.333
output += "\n\nbuf after deletes:\n" + buf.toString();
JOptionPane.showMessageDialog( null, output,
"Demonstrating StringBufferer Inserts and Deletes",
JOptionPane.INFORMATION_MESSAGE );
System.exit( 0 );
}
}
8.
// 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 + "\ns2 = " + s2 +
"\ns3 = " + s3 + "\ns4 = " + s4 + "\n\n";
//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\"\n";
else
output += "s1 does not equal \"hello\"\n";
// 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\"\n";
else
output += "s1 does not == \"hello\"\n";
// test for equality--ignore case
if ( s3.equalsIgnoreCase( s4 ) )
output += "s3 equals s4\n";
else
output += "s3 does not equal s4\n";
// 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 +=
"\ns1.compareTo( s2 ) is " + s1.compareTo( s2 ) +
"\ns2.compareTo( s1 ) is " + s2.compareTo( s1 ) +
"\ns1.compareTo( s1 ) is " + s1.compareTo( s1 ) +
"\ns3.compareTo( s4 ) is " + s3.compareTo( s4 ) +
"\ns4.compareTo( s3 ) is " + s4.compareTo( s3 ) +
"\n\n";
// 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\n";
else
output +=
"First 5 characters of s3 and s4 do not match\n";
// 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 );
}
}
/**************************************************************************
* (C) Copyright 1999 by Deitel & Associates, Inc. and Prentice Hall. *
* All Rights Reserved. *
* *
* 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. *
*************************************************************************/
9.
// 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 +
"\ns2 = " + s2;
output += "\n\nResult of s1.concat( s2 ) = " +
s1.concat( s2 );
output += "\ns1 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 +
"\ns2 = " + s2 +
"\ns3 = " + s3 +
"\ns4 = " + s4 +
"\ns5 = " + s5 +
"\ns6 = " + s6 +
"\ns7 = " + 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() +
"\nThe 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 += "\n'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 += "\n'$' is located at index " +
letters.indexOf( '$' );
// test lastIndexOf to find a character in a string
output += "\n\nLast 'c' is located at index " +
letters.lastIndexOf( 'c' );
output += "\nLast 'a' is located at index " +
letters.lastIndexOf( 'a', 25 );
output += "\nLast '$' is located at index " +
letters.lastIndexOf( '$' );
// test indexOf to locate a substring in a string
output += "\n\n\"def\" is located at index " +
letters.indexOf( "def" );
output += "\n\"def\" is located at index " +
letters.indexOf( "def", 7 );
output += "\n\"hello\" is located at index " +
letters.indexOf( "hello" );
// test lastIndexOf to find a substring in a string
output += "\n\nLast \"def\" is located at index " +
letters.lastIndexOf( "def" );
output += "\nLast \"def\" is located at index " +
letters.lastIndexOf( "def", 25 );
output += "\nLast \"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 += "\nLength of s1: " + s1.length();
// loop through the characters in s1 and display reversed
output += "\nThe 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 += "\nThe 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\"\n";
output += "\n";
// 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\n";
output += "\n";
// Test method endsWith
for ( int i = 0; i < strings.length; i++ )
if ( strings[ i ].endsWith( "ed" ) )
output += "\"" + strings[ i ] +
"\" ends with \"ed\"\n";
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 ) +
"\npart of char array = " +
String.valueOf( charArray, 3, 3 ) +
"\nboolean = " + String.valueOf( b ) +
"\nchar = " + String.valueOf( c ) +
"\nint = " + String.valueOf( i ) +
"\nlong = " + String.valueOf( l ) +
"\nfloat = " + String.valueOf( f ) +
"\ndouble = " + String.valueOf( d ) +
"\nObject = " + 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 ) + "\"\n";
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() +
"\nThe tokens are:\n" );
while ( tokens.hasMoreTokens() )
output.append( tokens.nextToken() + "\n" );
}
}
);
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 );
}
}
);
}
}
