叮当小马

摘要： import java.io.*; public class FileTest { public static void main(String[] args) { // TODO Auto-generated method stub File file = new File("E:/workspace/Java从入门到精通/mynote.txt"); if(file.exists()) { file.delete(); System.out.println("文件已经删除。"); } else { try{ file.createNewFile(); System.out.println("文件已经创建。"); }catch(Exception e) { e.printStackTrace(); } } } } 阅读全文

摘要： import java.util.*; //导入类 public class MapTest { /** * @param args */ public static void main(String[] args){ Map map = new HashMap(); Emp emp = new Emp("001","张三"); Emp emp2 = new Emp("005","张四"); //创建emp对象 Emp emp3 = new Emp("004","王一"); map.put(emp.getE_id(), emp.getE_name()); map.put(emp2.getE_id(), emp2.getE_name()); map.put(emp3.getE_id(), emp3.getE_name()); Set set = map.keySet(); Iterator it = set.iterator(); System.out.println( 阅读全文

摘要： import java.util.*; //导入类 public class ListGather { /** * @param args */ public static void main(String[] args) { List list = new ArrayList(); //集合类 list.add("a"); list.add("b"); list.add("c"); int i = (int)(Math.random()*(list.size()-1)); //0-2 System.out.println("随机获得数组中的元素："+list.get(i)); for(int j =0;jlist.size();j++) //循环遍历集合 { System.out.println(list.get(j)); } } } 阅读全文

摘要： import java.text.DecimalFormat; import java.util.Random; public class DecimalFormatDemo { /** * 简单格式化 * @param pattern * @param value */ public static void SimpleFormat(String pattern,double value) { DecimalFormat myFormat = new DecimalFormat(pattern); String output = myFormat.format(value); System.out.println(value + " "+ pattern + " "+ output); } /** * 使用applyPattern()方法对数字进行格式化 * @param pattern * @param value */ static public void UseApplyP 阅读全文

摘要： public class JavaType { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub //summation String str[] = {"89","12","10","18"}; int sum = 0; for(int i=0;istr.length;i++) { int myint = Integer.parseInt(str[i]); sum += myint; } System.out.println("数组中的各种元素之和为："+ sum); //charac String str1 = Integer.toString(456); String str2 = Integer.toBinaryString(456); String str3 = Integer.toHexString(456); 阅读全文

摘要： import java.util.Arrays; public class JavaArray { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub //创建一维数组： int arr[] = new int[]{1,2,3,5,15}; int arr2[] = {23,12,6}; int day[] = new int[]{31,28,31,30,31,30,31,30,31,30,31,31}; for(int i=0;i12;i++) { System.out.println((i+1)+"月有"+day[i]+"天"); } //二级数组： //int a[][] = new int[2][]; //a[0] = new int[2]; //a[1] = new int[3]; int a[][] = new int[][] 阅读全文

摘要： import java.util.Date; public class JavaString { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub //char to string char a[] = {'g','o','o','d','.'}; String s = new String (a); //全部字符 System.out.println(s); String ss = new String (a,2,2);//部分字符 System.out.println(ss); //多个字符串连接 String s1 = new String ("Hello"); String s2 = new String ("World"); String sss = s1 + " "+ s2; System.out.println(sss); 阅读全文

摘要： public class GetIfElse { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub //if语句 int x = 45; int y = 12; if(xy) { System.out.println("变量xy"); } if(x30) { System.out.println("z30"); }else if(z10) { System.o 阅读全文

摘要： public class MyNumber { static String s1="您好。"; public static void main(String[] args) { // TODO Auto-generated method stub String s2 = "Java"; System.out.println(s1); System.out.println(s2); //byte short int long byte mybyte = 124; //-128-127 short myshort = 32564; //-32768 - 32767 int myint=45784612; long mylong = 46789451; long result = mybyte + myshort +myint + mylong; System.out.println("结果为：" + result); // float double; float f1 = 13.23f 阅读全文

摘要： HelloJava 阅读全文