java 基础之String

String

charAT():提取指定字符
codePointAt(): 提取缩印字符串转为数字
codePointBefore(): 提取索引字符串的前一个字符转为数字
codePointCount(a,b): 返回a,b 之间的Unicode 的个数
a.compareTo(b) :比较a,b的大小 a>b:1 a=b:0 a<b:-1 返回int类型 (注：只能是string比较)
compareToIgnoreCase(): 忽略大小写比较
concat :字符串拼接：（不能指定位置）
contains（String ）:判断是否包含指定字符。 返回bool值 注：只能与string匹配
String.copyValueOf(arry) ; ：char数组转String
String.copyValueOf(arry,1,1); 第一个offset 第二个count
boolean endsWith(string) : 判断结尾字符串
boolean startsWith(string offset) offset可有可无： 判断字符串开端
boolean equals(object) : 万物皆可比 但方法只能String用
boolean equalsIngoreCase(String) : 只能与String 比较
String str = String.format()

（b:boolean    s:string   c:char  x:16   o:8   d:10进制   e：科学计数    %%：% ）

    public static void main(String[] args) {
        String strCom = "i like java";
        String strCom2 = "happy every day ";
        int strLower = strCom.codePointAt(5);
        int strLowerb = strCom.codePointBefore(5);
        int strLowerCount = strCom.codePointCount(2,5);
        System.out.println(strLower);
        System.out.println(strLowerb);
        System.out.println(strLowerCount);
        System.out.println((char)101);
        System.out.println((char)107);
        int  n1 = strCom.compareTo(strCom2);
        System.out.println(n1);
//        cha,int汇报错
//        int c1 =1 ,c2 =3;
//        System.out.println(c1.compareTo(c2));
        System.out.println(strCom.concat(strCom2));
        System.out.println(strCom.contains("java1"));
        char[] arry = {'i','o','k'};
        String str = String.copyValueOf(arry,1,1);
        System.out.println(str);
        boolean b2 = strCom.equals(n1);
        System.out.println(b2);
        boolean b3 = strCom.equalsIgnoreCase(strCom2);
        String formatDemo = String.format("hello %s,my name is %s,my age is %d","world",             注意写法：  %d表示数字
                "huluwa",19);
        System.out.println(formatDemo);
        String str1 = String.format("%d",400/2);
        String str2 = String.format("%b",3>4);
        System.out.println(str1);
        System.out.println(str2);

}

　String  str=   String.format(local i , String format,args);   %te  tb/tB  tA/ta  tc  tY tj   tm  td  ty

 Date date = new Date();
        Locale form = Locale.CHINA;
        String year = String.format(form,"%tY",date);
        String month  = String.format(form,"%tb",date);
        String day = String.format(form,"%td",date);

        System.out.println(year+month+day);

getBytes()      str1 = strCom.getBytes("utf-8"); 注意要catch以下  否则会报错               str1 = strCom.getBytes(Charset.defaultCharset());   虚拟机默认的byte序列

        String strCom = "java";
        byte[]  str= strCom.getBytes();
        System.out.println(str);

        for (int i = 0;i<str.length;i++)
        {
            System.out.println(str[i]);
        }
    }

getChars(str第一个索引  strend索引   数组   数组偏移量)

     String strCom = "l Like Java";
        char[] dst = new char[10];
        strCom.getChars(0,10,dst,0);
        for (int i=0;i<dst.length;i++)
        {
            System.out.println(dst[i]);
        }

 hashCode()

      String str = "i happy ";
        int n = str.hashCode();
        System.out.println(n);
        String str1 = " mima123456";
        int n1 = str1.hashCode();
        String str2 = "123456";
        int n2 = str2.hashCode();
        System.out.println(n1);
        System.out.println(n2);

indexof(  ,offset )   可以有偏移量

    int index = str.indexOf("ha");
        int index1 = str.indexOf(5);
        int index2 = str.indexOf('a');
        System.out.println(index+"+"+index1+"+"+index2);

string   intern()     类似python  数据池

  String str1 = new String("I LIKE JAVA");
        String str2 = new String("I LIKE JAVA");
        System.out.println(str1.equals(str2));
        System.out.println(str1==str2);
        System.out.println(str1.intern()==str2.intern());
        System.out.println(str1+'+'+str2);

boolean     isEmpty ()                                  int     lastIndexOf():可以设置formIndex                       .length()

matches():正则匹配

offsetByCodePoints()；获取索引便宜后指定代码的索引

 String str = "I LIKE JAVA";
        int i = str.offsetByCodePoints(2,3);
        System.out.println(i);
        
        //会报错 索引超出范围
//        int i = str.offsetByCodePoints(9,3);
//        System.out.println(i);

boolean   regionMatches(bool :是否忽略大小写 , 偏移量   ,otherstring  ,otherstroffset   ,len ):测试两个字符串区域是否相等       比较指定两个区域之间字符串是否相当等

   String str = "I LIKE JAVA";
        int i = str.offsetByCodePoints(2,3);
        System.out.println(i);
        String st2 = "hello  world   happy every day ";
        String st3 = "hello  world   happy  day ";

       boolean b1 =  str.regionMatches(true,0,st2,0,10);
       boolean b2 =  st2.regionMatches(true,0,st3,0,10);
        System.out.println(b1);
        System.out.println(b2);
    }

repalce   repalceAll()

String  str = "i like java everyday 666";
String str1 = str.replace('a','6');
String str2 = str.replace("ava","AVA");
System.out.println(str1);
System.out.println(str2);


String str4 = str.replace(" ","WOW!");
System.out.println(str4);

string[]    split()       :  注意返回的是      string[ ]    不是char[]

        String str = "公司名称:明日科技!公司所正在城市:长春市。公司电话:84972266";
        String[] liststr = str.split("!|。");     注意 ：如果是.需要//.
        String[] liststr1 = str.split(":");
        for (int i=0;i<liststr.length;i++)
        {
            System.out.println(liststr[i]);

        }

        System.out.println("-----------------------");
        for (int i=0;i<liststr1.length;i++)
        {
            System.out.println(liststr1[i]);

        }