API 文档

String Builder and String Buffer

1. package org.forten.api.string;
   
   public class StringBuilderTest001 {
    public static void main(String[] args) {
        StringBuilder sb1 = new StringBuilder("abc");
        sb1.append("de").append("fghi").append("jklmn");
        System.out.println(sb1.toString());
        
        sb1.reverse();
        System.out.println(sb1.toString());
        sb1.reverse().insert(3, " true ");
        System.out.println(sb1.toString());
        
        sb1.delete(3, 9);
        System.out.println(sb1.toString());
        
        sb1.deleteCharAt(1);
        System.out.println(sb1.toString());
        
        StringBuilder sb2 = new StringBuilder("abc ade axy");
        sb2.replace(0, sb2.length()-5, "123");
        System.out.println(sb2.toString());
        sb2.replace(0, sb2.length(), "123");
        System.out.println(sb2.toString());
        
        StringBuilder sb3 = new StringBuilder("天生我才有用，This is an orange.");
        String s1 = sb3.substring(7);
        System.out.println(s1);
        String s2 = sb3.substring(2,6);
        System.out.println(s2)；
               //当使用StringBuilder(String str)构造StringBuilder对象的时候，对象的容量是str的长度加16
               System.out.println(sb3.capacity());//25+16=41
           //把StringBuilder对象中空余空间释放，只留存已有字符数据的部分
           sb3.trimToSize();// 41 - 16 = 25
        System.out.println(sb3.capacity());// 25
    }
   }
   

2. package org.forten.api.string;
   
   import java.util.Arrays;
   
   public class StringTest004 {
    public static void main(String[] args) {
        String s1 = "abc";
        String s2 = new String("abc");
        String s3 = new String("abcde");
        String s4 = new String("bc");
        String s5 = new String("Abc");
   
            //str1.compareTo(str)
            //按字典顺序比较str1和str2,A<Z<a<z,但此方法不会忽略大小写
            System.out.println(s1.compareTo(s2));
        System.out.println(s2.compareTo(s3));
        System.out.println(s2.compareTo(s4));
        System.out.println(s1.compareTo(s5));
        //s1.compareToIgnoreCase(s2)
        //是大小写不敏感的字符串比较
        System.out.println(s1.compareToIgnoreCase(s5));
   
   
   
            //s1.concat(s5)=>s1+s5
            s3 = s1.concat(s5);
        s4 = s1 + s5;
        System.out.println(s3);
        System.out.println(s4);
   
        s1 = "def";
        s2 = "abcdefgxyz";
        s3 = "ab";
        s4 = "yz";
        //判定一个字符串是否以另一个字符串开始
        System.out.println(s2.startsWith(s3));
        //判定一个字符串是否以另一个字符串结束
        System.out.println(s2.endsWith(s4));
        //判定一个字符串是否包含另一个字符串
        System.out.println(s2.contains(s1));
        
        
        s1 = "abcdeabcdexyzabcd";
        //使用indexof()方法可以替代以下两个参数的startWith()
        System.out.println("abc".startsWith("cde", 12));
        //int indexof(String str)
        //在大串中查找参数str从左向右顺序，第一次出现的索引位置，如果str不存在于大串中，返回-1
        //int indexOf(String str,int fromIndex)
        //在大串中，使用fromIdex字符处开始查找参数str，方向是从左向右顺序，第一次出现的索引位置，如果str不存在于大串中，返回-1
        //通常使用此方法查询某个子串是否存在于大串中，用是否返回-1判定
        System.out.println(s1.indexOf("cd"));
        System.out.println(s1.indexOf("cd", 10));
        System.out.println(s1.indexOf("cdz"));
        System.out.println(s1.indexOf("cdz", 10));
        System.out.println("----------------------------------");
        
        //lastIndexOf方法与indexOf方法大致相同，只是方向是从右向左进行查找的
        System.out.println(s1.lastIndexOf("cd"));
        System.out.println(s1.lastIndexOf("cd", 10));
        System.out.println(s1.lastIndexOf("cdz"));
        System.out.println(s1.lastIndexOf("cdz", 10));
   
        s1 = String.format("%s今年%d岁了，是%s年上的班，工资目前是%f", "张小飞", 32, "2010", 15000.5);
        System.out.println(s1);
        s1 = String.format("%3$s今年%1$d岁了，是%2$s年上的班，工资目前是%4$f", 32, "2010", "张小飞", 15000.5);
        System.out.println(s1);
   
        System.out.printf("%s今年%d岁了，是%s年上的班，工资目前是%f%n", "张小飞", 32, "2010", 15000.5);
   
        System.out.println("abc");
        //indet(n)缩进n个空格，并在字符串后加入换行
        ystem.out.print("[" + "abc".indent(4) + "]");
        System.out.print("[" + "abc".indent(8) + "]");
        System.out.println("----------------------------------");
        //空串、只是由空白符构成的字符串在调用isBlank()方法后会返回true，否则返回false
        System.out.println("".isBlank());
        System.out.println("   ".isBlank());
        System.out.println("\t\n \r".isBlank());
        System.out.println("\t\na\r".isBlank());
        String nullStr = null;
        //System.out.println(nullStri.isBlank());
        
        //只有字符串的长度是0时，isEmpty()方法才返回true，与字符串内容是否时空白符无关
        System.out.println("".isEmpty());
        System.out.println("   ".isEmpty());
        System.out.println("\t\n \r".isEmpty());
        System.out.println("\t\na\r".isEmpty());
        System.out.println("   ".trim().isEmpty());
        System.out.println(" a b c  ".trim().isEmpty());
   
        System.out.println("----------------------------------");
        
        //使用第一个参数作为分隔符，把后续的可变长参数连接成一个字符串
        String[] strArr = { "abc", "星垂平野阔", "apple", "3.1415926", "十一不放假", "春假吃卤煮", "Java得永生" };
        s1 = String.join(" --- ", strArr);
        System.out.println(s1);
        s1 = String.join(", ", "abc", "星垂平野阔", "apple", "3.1415926", "十一不放假", "春假吃卤煮", "Java得永生");
        System.out.println(s1);
   
        System.out.println("----------------------------------");
   
        System.out.println("abcdefg".length());
        System.out.println("星垂平野阔春假吃卤煮".length());
   
        //lines()方法会将字符串以回车换行分隔为若干元素并组织成一个Stream
        "abc\nxyz\n123\n春假吃卤煮".lines().forEach(System.out::println);
   
        System.out.println("15263".matches("\\d+"));
        System.out.println("-15263".matches("-\\d+"));
        System.out.println("abc123XYZ".matches("\\w+"));
        System.out.println("\t\n ".matches("\\s+"));
        System.out.println("15263".matches("\\D+"));
        System.out.println("abc123XYZ".matches("\\W+"));
        System.out.println("\t\n ".matches("\\S+"));
   
        System.out.println("----------------------------------");
   
        //str.repeat(n)让str重复n次组成一个新的字符串
        s1 = "abc, 星垂平野阔, apple, 3.1415926, 十一不放假, 春假吃卤煮, Java得永生";
        strArr = s1.split(", ");
        System.out.println(strArr.length);
        Arrays.stream(strArr).forEach(System.out::println);
        System.out.println("----------------------------------");
        strArr = s1.split(", ", 5);
        System.out.println(strArr.length);
        Arrays.stream(strArr).forEach(System.out::println);
    System.out.println("----------------------------------");
    
    System.out.println("[" + "  abc   ".strip() + "]");
        System.out.println("[" + "  abc   ".trim() + "]");
        System.out.println("[" + "     ".strip() + "]");
        System.out.println("[" + "     ".trim() + "]");
        System.out.println("[" + " \n ".strip() + "]");
        System.out.println("[" + " \n ".trim() + "]");
        System.out.println("[" + "  abc   ".stripLeading() + "]");
        System.out.println("[" + "  abc   ".stripTrailing() + "]");
   
        System.out.println("----------------------------------");
   
        //
        s1 = "abcdefghijklmn";
        
        //从s1的第11个字符开始截取到s1的结束
        s2 = s1.substring(10);
        System.out.println(s2);
        //从s1的第四个字符开始截取到第7个字符之前
        s2 = s1.substring(3, 6);
        System.out.println(s2);
        
        String sb = (String)s1.subSequence(3, 6);
        System.out.println(sb);
        
        System.out.println("This Is An Apple.".toUpperCase());
        System.out.println("This Is An Apple.".toLowerCase());
    }
   }
    
        
        
        
        
   
   

3. package org.forten.api.date;
   
   import java.util.Date;
   
   public class DateTest001 {
    public static void main(String[] args) {
    //Date()构造器得到的对象描述着执行此构造器时的提起时间点
    Date currentTime = new Date();
        System.out.println(currentTime);
   
        long ms = 10 * 365 * 24 * 60 * 60 * 1000L;
        //Date(long ms),得到从1970年元旦0点经过ms毫秒后的时间点
        Date d = new Date(ms);
        System.out.println(d);
        
        
        //当前时间与1970年元旦0点之间的毫秒差
        //new Date(System.currentTimeMillis())与new Date()有作用类似
        System.out.println(System.currentTimeMillis());
        //getTime()得到提起对象与1970年元旦0点之间的毫秒差
        System.out.println(currentTime.getTime()); 
    }
   }
   
   package org.forten.api.date;
   
   import java.util.Calendar;
   import java.util.Date;
   
   public class DateTest002 {
    public static void main(String[] args) {
        Calendar cal1 = Calendar.getInstance();
        System.out.println(cal1);
   
        cal1.set(2019, 0, 1, 0, 0, 0);
        System.out.println(cal1);
   
        cal1.set(Calendar.YEAR, 2010);
        cal1.set(Calendar.MONTH, Calendar.AUGUST);
        cal1.set(Calendar.DAY_OF_MONTH, 25);
        cal1.set(Calendar.HOUR, 3);
        cal1.set(Calendar.MINUTE, 15);
        cal1.set(Calendar.SECOND, 32);
        System.out.println(cal1);
        
        Date date = new Date(20 * 365 * 24 * 60 * 60 * 1000L);
        cal1.setTime(date);
        System.out.println(cal1);
        Calendar cal2 = Calendar.getInstance();
        cal2.setTimeInMillis(20 * 365 * 24 * 60 * 60 * 1000L);
        System.out.println(cal1.equals(cal2));
        
        cal1.add(Calendar.YEAR, 50);
        cal1.add(Calendar.MONTH, -3);
        System.out.println(cal1);
    }
   }