java教材源代码第7章 Java常用系统类.docx

1、java教材源代码第7章 Java常用系统类第7章 Java常用系统类 【例7-1】求指定字符串的长度。public class StrLength public static void main(String args) String s1=Hello,Java!; String s2=new String(你好,Java); int len1=s1.length(); int len2=s2.length(); System.out.println(字符串s1长度为+len1); System.out.println(字符串s2长度为+len2); 【例7-2】字符串比较中=运算符的使用。

2、public class StrEqual public static void main(String args) String s1 = Java;String s2 = Java;if (s1 = s2)System.out.println(s1 = s2);elseSystem.out.println(s1 != s2); 【例7-3】字符串对象变量间的赋值运算。public class StrEqual_1 public static void main(String args) String s1 = Java;String s2;s2=s1;if (s1 = s2) System

3、.out.println(s1 = s2); elseSystem.out.println(s1 != s2); 【例7-4】在字符串比较中=运算符与equals方法的使用。public class StrEqual_2 public static void main(String args) String s1 = Java; String s2 = new String(Java); if (s1 = s2) System.out.println(s1 = s2);else System.out.println(s1 != s2);if (s1.equals(s2) System.out.

4、println(s1 equals s2);elseSystem.out.println(s1 not equals s2); 【例7-5】字符串intern()方法的使用。public class StrEqual_3 public static void main(String args) String s1 = Java; String s2 = new String(Java); s2 = s2.intern(); if (s1 = s2) System.out.println(s1 = s2); else System.out.println(s1 != s2); if (s1.eq

5、uals(s2) System.out.println(s1 equals s2); else System.out.println(s1 not equals s2); 【例7-6】使用+和concat方法创建同一个字符串。public class StrConcatpublic static void main(Srting args) String s1=Hello; String s2=s1+,; String s3=s2.concat( Java);! String s4=new String( ! ); String s5=s3.concat(s4); System.out.pri

6、ntln( 连接而成的字符串是+s5); 【例7-7】复制字符串。public class StrCopypublic static void main(String args) String s1=new String( ); char data = a, b, c, d, e, f; s1=String.copyValueOf(data); System.out.println( s1=+s1); s1=String.copyValueOf(data,2,3); System.out.println( s1=+s1); s1.getChars(1,2, data,0) System.out

7、.println( data=+String.copyValueOf(data); data=s1.toCharArray( ); System.out.println( data=+String.copyValueOf(data); String s2=new String( ); String s3=new String( ); s2=s1.substring(0); System.out.println( s2=+s2); s3= s1.substring(1,2); System.out.println( s3=+s3); 【例7-8】在字符串中查找字符和子串。public class

8、 StrSearchpublic static void main(String args) String s1=Javav; char c=s1.charAt(2); System.out.println(c=,+c); int i=s1.indexOf(a); System.out.println(fistchar=,+i); int j=s1.lastIndexOf(a); System.out.println(lastchar=,+j); i= s1.indexOf(av); System.out.println(fiststring=,+i); j=s1.lastIndexOf(av

9、); System.out.println(laststring=,+j); 【例7-9】重写toString()方法，输入两个字符串的连接。import java.io.*;public class TestString public static void main(String args) StringC s = new StringC(cool,java); System.out.println(s); class StringC String s1;String s2;StringC(String str1,String str2) s1 = str1; s2 = str2; pub

10、lic String toString() return s1+s2; 【例7-10】用多种方法创建StringBuffer对象。public class StrBufferSetpublic static void main(String args)StringBuffer s1=new StringBuffer( );s1.append(Hello,Java!);System.out.println(s1= +s1);StringBuffer s2=new StringBuffer(10 );s2.insert(0, Hello,Java!);System.out.println(s2=+

11、s2);StringBuffer s3=new StringBuffer(Hello,Java!);System.out.println(s3=+s3); 【例7-11】显示确定字符串的长度和容量，并改变字符串的长度。public class StrLenpublic static void main(String args)StringBuffer s1=new StringBuffer(Hello,Java!);System.out.println(长度：+s1.length( );System.out.println(容量：+s1.capacity( );s1.setLength(100

12、);System.out.println(新长度：+s1.length( ); 【例7-12】改变字符串的内容。public class StrChangepublic static void main(String args)StringBuffers1=new StringBuffer(Hallo,Java!);s1.setCharAt(1, e);System.out.println(s1);s1.replace(1,5, i);System.out.println(s1);s1.delete(0,3);System.out.println(s1);s1.deleteCharAt(4);

13、System.out.println(s1); 【例7-13】分析给定字符串，分别输出字符串的单词，并统计出单词个数。import java.util.*;public class TokenDemopublic static void main(String args) String s=I am Geng.X.y,she is my girlfriend; StringTokenizer fenxi=new StringTokenizer(s, ,); int number=fenxi.countTokens(); while(fenxi.hasMoreTokens() String st

14、r=fenxi.nextToken(); System.out.println(str); System.out.println(还剩+fenxi.countTokens()+个单词); System.out.println(s 共有单词 +number+个); 【例7-14】编程实现两个随机的10以内的整数加法运算题目，共10道题目，要求从键盘输入运算结果，最终显示计算正确的题目数。import java.io.*;public class MathDemo public static void main(String args) int count=0; for(int i=1;i=10;i+) int num1,num2,sum=0; num1=(