String 类
Strng 类举例(1)
String 类常用方法(1)
String 类常用方法(2)
String 类常用方法(3)
练习
import java.util.regex.*; public class TestString { public static void main(String[] args) { //String s = "AaaaABBBBcc&^%adfsfdCCOOkk99876 _haHA"; //int lCount = 0, uCount = 0, oCount = 0; /* for(int i=0; i<s.length(); i++) { char c = s.charAt(i); if(c >= ‘a‘ && c <= ‘z‘) { lCount ++; } else if (c >=‘A‘ && c <= ‘Z‘) { uCount ++; } else { oCount ++; } } */ /* String sL = "abcdefghijklmnopqrstuvwxyz"; String sU = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; for(int i=0; i<s.length(); i++) { char c = s.charAt(i); if(sL.indexOf(c) != -1) { lCount ++; } else if (sU.indexOf(c) != -1) { uCount ++; } else { oCount ++; } } */ /* for(int i=0; i<s.length(); i++) { char c = s.charAt(i); if(Character.isLowerCase(c)) { lCount ++; } else if (Character.isUpperCase(c)) { uCount ++; } else { oCount ++; } } System.out.println(lCount + " " + uCount + " " + oCount); */ String s = "sunjavahpjavaokjavajjavahahajavajavagoodjava"; String sToFind = "java"; int count = 0; int index = -1; while((index = s.indexOf(sToFind)) != -1) { s = s.substring(index + sToFind.length()); //找到的位置+字符串的长度 count ++; } System.out.println(count); } }
TestString.java
StringBuffer类
StringBuffer常用方法
基本数据类型包装类
包装类常见方法
练习
public class ArrayParser { public static void main(String[] args) { double[][] d; String s = "1,2;3,4,5;6,7,8"; String[] sFirst = s.split(";"); d = new double[sFirst.length][]; for(int i=0; i<sFirst.length; i++) { String[] sSecond = sFirst[i].split(","); d[i] = new double[sSecond.length]; for(int j=0; j<sSecond.length; j++) { d[i][j] = Double.parseDouble(sSecond[j]); } } for(int i=0; i<d.length; i++) { for(int j=0; j<d[i].length; j++) { System.out.print(d[i][j] + " "); } System.out.println(); } } }
ArrayParser.java
Math类举例
File 类
package bjsxt; import java.io.*; public class TestFile { public static void main(String[] args) { String separator = File.separator; String filename = "myfile.txt"; String directory = "mydir1" + separator + "mydir2"; //String directory = "mydir1/mydir2"; //String directory = "mydir1\\mydir2"; File f = new File(directory, filename); if (f.exists()) { System.out.println("文件名:" + f.getAbsolutePath()); System.out.println("文件大小:" + f.length()); } else { f.getParentFile().mkdirs(); try { f.createNewFile(); } catch (IOException e) { e.printStackTrace(); } } } }
TestFile.java
import java.io.*; public class FileList { public static void main(String[] args) { File f = new File("d:/A"); System.out.println(f.getName()); tree(f, 1); } private static void tree(File f, int level) { String preStr = ""; for(int i=0; i<level; i++) { preStr += " "; } File[] childs = f.listFiles(); for(int i=0; i<childs.length; i++) { System.out.println(preStr + childs[i].getName()); if(childs[i].isDirectory()) { tree(childs[i], level + 1); } } } }
FileList.java
Java.lang.Enum枚举类型
public class TestEnum { public enum MyColor { red, green, blue }; public enum MyDoorOpener {me, mywife}; public static void main(String[] args) { MyColor m = MyColor.red; switch(m) { case red: System.out.println("red"); break; case green: System.out.println("green"); break; default: System.out.println("default"); } System.out.println(m); } }
TestEnum.java
时间: 2024-07-29 01:47:04