数组与字符串(基础篇).ppt

第六章 数组与字符串,6.1 数组 6.2 字符串,6.1 数组,数组的创建(一维数组和二维数组；基本数据类型和复合数据类型） 指定数组名称、数据类型 type var_name; 如：char s; Object o; int i;,6.1 数组,为数组分配内存空间 var_name = new typesize; 如：s = new char30; o = new Object2; o0 = new Object(); o1 = new Object(); i = new int23; char s = new char30; 初始化 int i1 = 1,1,2,3,6.1 数组,数组的使用(一维数组和二维数组；基本数据类型和复合数据类型） 数组元素表示： 数组名下标， 数组名下标1下标2 , 数组名0数组名n-1 Length域 一元数组元素的复制 =； System.arraycopy(from fromIndex,to,toIndex,count),6.1 数组示例1,/ InitArray.java: initializing an array import java.io.*; public class InitArray public static void main( String args ) int n = new int 10 ; for ( int i = 0; i n.length; i+ ) System.out.print( i + “t“ + n i + “n “); ,6.1 数组示例2,/ InitArray.java import java.io.*; public class InitArray public static void main( String args ) int n = 32, 27, 64, 18, 95, 14, 90, 70, 60,37 ; for ( int i = 0; i n.length; i+ ) System.out.print( i + “t“ + n i + “n“); ,6.1 数组示例3,/ InitArray.java import java.io.*; public class InitArray public static void main( String args ) final int ARRAY_SIZE = 10; int n = new int ARRAY_SIZE ; for ( int i = 0; i n.length; i+ ) n i = 2 + 2 * i; for ( int i = 0; i n.length; i+ ) System.out.print( i + “t“ + n i + “n“); ,/ BubbleSort.java import java.applet.*; public class BubbleSort extends Applet public void init() int a = 2, 6, 4, 8, 10, 12, 89, 68, 45, 37 ; for ( int i = 0; i a.length; i+ ) System.out.print( a i + “ “ ); System.out.println( ); bubbleSort( a );,6.1 数组示例4（排序）,6.1 数组示例4,for ( int i = 0; i b i + 1 ) swap( b, i, i + 1 ); public void swap( int c, int first, int second ) int hold; hold = c first ;,c first = c second ; c second = hold; public void bubbleSort( int b ) for ( int pass = b.length - 1; pass 0; pass- ) for ( int i = 0; i b i + 1 ) swap(b,i,i + 1); ,6.1 数组示例4,/ JavaArrayUse.java public class JavaArrayUse public static void main( String args ) int i,j; int youngMaxLevel = 15; int young; young = new intyoungMaxLevel; for ( i = 0; i young.length; i+ ) youngi = new inti+1; young0 0 = 1;,6.1 数组示例4(杨辉三角型）,for ( i = 1; i young.length; i+ ) youngi0 = 1; for ( j = 1; j youngi.length-1; j+ ) youngij = youngi-1j-1+youngi-1j; youngiyoungi.length-1 = 1; for ( i = 0; i young.length; i+ ) for ( j = 0; j youngi.length; j+ ) System.out.print(youngij+“ “); System.out.println(); ,6.1 数组示例4,6.1 数组示例6（读程序）,import java.applet.Applet; public class PassArray extends Applet public void init() int a = 1, 2, 3, 4, 5 ; for ( int i = 0; i a.length; i+ ) System.out.print ( a i + “ “ ); System.out.println( ); modifyArray( a ); for ( int i = 0; i a.length; i+ ) System.out.print( a i + “ “ ); System.out.println( );,6.1 数组示例6（读程序）,modifyElement( a 3 ); System.out.print( a 3 ); public void modifyArray( int b ) for ( int j = 0; j b.length; j+ ) b j *= 2; public void modifyElement( int e ) e *= 2; ,6.1 数组示例7,/ Test.java public class Test public static void main( String args ) Point point = new Point( 7, 11 ); Circle circle = new Circle( 3.5, 22, 8 ); Cylinder cylinder = new Cylinder( 10, 3.3, 10, 10 ); Shape arrayOfShapes; arrayOfShapes = new Shape 3 ; arrayOfShapes 0 = point;,6.1 数组示例7,arrayOfShapes 1 = circle; arrayOfShapes 2 = cylinder; for ( int i = 0; i arrayOfShapes.length; i+ ) System.out.println(“nn“ + arrayOfShapes i .getName() + “: “ + arrayOfShapes i .toString() ) ,6.2 字符串,创建字符串 使用字符串,1. 创建字符串,方法1：new方法 String str = new String(); String str = new String( This is a string ); StringBuffer str = new StringBuffer(10); 方法2：初始化方法 String str =This is a string; String str ; str = This is a string ; 字符串常量： hello world ,例1：构造方法,/ StringConstructors.java public class StringConstructors public static void main( String args ) char charArray = b, i, r, t; byte byteArray = (byte) n, (byte) e, (byte) w, (byte) r ; String s, s1, s2, s3, s4, s5, s6; s = new String( “hello“ ); s1 = new String(); s2 = new String( s );,例1：构造方法,s3 = new String( charArray ); s4 = new String( charArray, 1, 2 ); s5 = new String( byteArray, 1, 2 ); s6 = new String( byteArray ); System.out.print(“s1 = “ + s1 + “ns2 = “ + s2 + “ns3 = “ + s3 +“ns4 = “ + s4 + “ns5 = “ + s5 + “ns6 = “ + s6 + “ns7 = “ + s7); ,例2：构造方法,public class StringBufferConstructors public static void main( String args ) StringBuffer buf1, buf2, buf3; buf1 = new StringBuffer(); buf2 = new StringBuffer( 10 ); buf3 = new StringBuffer( “hello“ ); System.out.println( buf1.toString() ); System.out.println(buf2.toString() ); System.out.println(buf3.toString() ); ,2. 使用字符串,String类 访问：length(),charAt(),indexof(), lastIndexof(), getChars(), getBytes()等 int len=str.length(); char c=str.charAt(i); int i = str.indexOf(a); int i = str.lastIndexOf(a); 修改：concat(),replace(),substring(), toLowerCase(), toUpperCase() 比较：equals(),equalsIgnoreCase(), CompareTo(), RegionMatches(),2. 使用字符串,StringBuffer 访问：length(),charAt(),getChars(), capacity(); int capa = str.capacity(); 修改：append(),insert(),setCharAt() str.append(“abc”); str.insert(4,“abc”); str.setChatAt(int,char); 字符串的转化 StringBuffer:toString():将可变字符串变成不变字符串 String:valueOf():将不同类型的数字转化为不变字符串 字符串的重载: +,例3：方法使用,/ StringCompare.java 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“ ); System.out.print( “s1 = “ + s1 + “ns2 = “ + s2 +“ns3 = “ + s3 + “ns4 = “ + s4 + “nn “);,例3：方法使用,if ( s1.equals( “hello“ ) ) System.out.print( “s1 equals “hello“n “); else System.out.print( “s1 does not equal “hello“n “); if ( s1 = “hello“ ) System.out.print( “s1 equals “hello“n “); else System.out.print( “s1 does not equal “hello“n “);,例3：方法使用,if ( s3.equalsIgnoreCase( s4 ) ) System.out.print( “s3 equals s4n “); else System.out.print( “s3 does not equal s4n “); System.out.print( “pareTo( s2 ) is “ + pareTo( s2 ) + “pareTo( s1 ) is “ + pareTo( s1 ) + “pareTo( s1 ) is “ + pareTo( s1 ) + “pareTo( s4 ) is “ + pareTo( s4 ) + “pareTo( s3 ) is “ + pareTo( s3 ) + “nn “);,例3：方法使用,if ( s3.regionMatches( 0, s4, 0, 5 ) ) System.out.print( “First 5 characters of s3 and s4 matchn “); else System.out.print( “First 5 characters of s3 and s4 do not matchn “); if ( s3.regionMatches( true, 0, s4, 0, 5 ) ) System.out.print( “First 5 characters of s3 and s4 match “); else System.out.print( “First 5 characters of s3 and s4 do not match ); ,例4：方法使用,public class Test String myString = “2”; public static void main(String args) Test myObj = new Test() myObj.stringModifier(myObj.myString); System.out.println(“ ” + myObj.myString); void stringModifier (String theString) theString = theString + “3”; System.out.print(theString); ,内容要点,数组的创建及使用 字符串的创建及使用,习题,随机产生十个数进行降序排序。 修改例子中的冒泡排序，以提高性能。 命令行参数的使用:从命令行输入需要排序的个数,将随机产生的数进行升序排序。 编写一个应用程序，读入 如07/21/1999格式的日期，打印出如July 21，1999格式的日期。 拼写检查器。,/ StringTest.java public class StringTest public static void main( String args ) String s = new String( “07/21/1999“ ); String s1 = s.substring(0,2); int m = Integer.parseInt( s1 ); switch(m) case 1 :System.out.print(“January “+ s.substring(3,5)+ “,“+s.substring(6,10); break;,case 2 :System.out.print(“February “+s.substring(3,5)+“,“+s.substring(6,10); break; case 3 :System.out.print(“