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]);

        }