Java中String類常用類型實(shí)例總結(jié)

更新時(shí)間：2021年12月24日 09:44:17 作者：Fly?upward

在我們開(kāi)發(fā)中經(jīng)常會(huì)用到很多的常用的工具類,這里做一個(gè)總結(jié),下面這篇文章主要給大家介紹了關(guān)于Java中String類常用類型的相關(guān)資料,String類代表字符串,需要的朋友可以參考下

1.創(chuàng)建字符串的方法

1.1構(gòu)造

方式一、直接構(gòu)造

String str = "fly";

方式二、調(diào)用構(gòu)造方法進(jìn)行構(gòu)造對(duì)象

String str1 = new String("name");

方式三、利用字符數(shù)組進(jìn)行轉(zhuǎn)換

char[] ch = {'a','s','d'};
String str2 = new String(ch);

1.2引用對(duì)象

    public static void main(String[] args) {
        //str 、 str1 都指向同一個(gè)對(duì)象
        String str = "asd";
        String str1 = str;
        System.out.println(str);
        System.out.println(str1);
        System.out.println("---------------");
 
        str = "fly";//str指向新的對(duì)象，str1 沒(méi)有變，還指著原來(lái)的對(duì)象
        System.out.println(str);
        System.out.println(str1);
 
    }

    public static void func(String s,char[] array) {
        s = "fly";
        array[0] = 'm';
 
    }
 
    public static void main(String[] args) {
        String str = "asfgh";
        char[] ch = {'w','s','d'};
        func(str,ch);
        System.out.println(str);
        System.out.println(Arrays.toString(ch));
 
    }

?2.字符串的比較

    public static void main(String[] args) {
        String str1 = "hello";
        String str2 = "hello";
        System.out.println(str1 == str2);
        System.out.println(str1.equals(str2));
    }

    public static void main(String[] args) {
        String str1 = "ABC";
        String str2 = "abc";
        boolean flg = str1.equalsIgnoreCase(str2);//不看大小寫判斷字符串是否相等
        System.out.println(flg);
    }

3.字符串的不可改變性

字符串是一種不可變對(duì)象 . 它的內(nèi)容不可改變

   public static void main(String[] args) {
        String str = "hello ";
        str = str + "world ";
        str += "!!!";
        System.out.println(str);
 
    }

4.數(shù)組轉(zhuǎn)字符串

   public static void main(String[] args) {
        char[] val = {'a','b','c','d','f'};
        String str = new String(val);
        String str2 = new String(val,1,3);//區(qū)間變字符串
        System.out.println(str);
        System.out.println("------------");
 
        String str3 = "hello";
        char ch = str3.charAt(2);//獲取下標(biāo)字符
        System.out.println(ch);
 
        char[] chars = str3.toCharArray();//把str3指向的字符串變?yōu)閿?shù)組
        System.out.println(Arrays.toString(chars));
 
 
    }

?5.判斷是否是數(shù)字字符串? isNumberChar(? )

    public static boolean isNumberChar(String s) {
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);//逐個(gè)獲取字符
            boolean flg = Character.isDigit(c);//判斷某個(gè)字符是不是數(shù)字
            if(flg == false) {
                return false;
            }
            /*if (c < '0' || c > '9') {
                return false;
            }*/
        }
        return true;
    }
 
    public static void main(String[] args) {
        String str = "0123456789";
        System.out.println(isNumberChar(str));
    }

?6.字節(jié)變字符串

    public static void main(String[] args) {
        byte[] bytes = {97,98,99,100};//字節(jié)對(duì)應(yīng)的字母
        String str = new String(bytes);
        System.out.println(str);
 
        String str2 = new String(bytes,1,3);
        System.out.println(str2);
        System.out.println("-------------");
        String str3 = "flying";
        byte[] bytes1 = str3.getBytes();//獲取字符對(duì)應(yīng)的字節(jié)
        System.out.println(Arrays.toString(bytes1));//以數(shù)組形式輸出
    }

?7.字符串的查找

    public static void main(String[] args) {
        String str = "babcdabcab";
        String str2 = "abc";
        boolean flg = str.contains(str2);//判斷是否含有子字符串
        System.out.println(flg);
        System.out.println("-----------");
 
        int index = str.indexOf(str2);//找出子字符串第一次開(kāi)始出現(xiàn)的位置
        System.out.println(index);
        System.out.println(str.lastIndexOf(str2,8));//從指定位置往前找
        System.out.println(str.startsWith("a"));//判斷是否是以其字母開(kāi)頭的字符串
        System.out.println(str.startsWith("a",1));//判斷某位置是否是該字母
        System.out.println(str.endsWith("ab"));//判斷是否是以該字符串結(jié)尾
    }

8.字符的替換

    public static void main(String[] args) {
        String str = "babcdabcab";
        String ret = str.replace('a','f');//將所有字符a替換成f
        //String ret = str.replaceFirst('a','f');//將第一次出現(xiàn)的字符a替換成f
        System.out.println(ret);
    }

9.字符串的分割

9.1以單個(gè)符號(hào)來(lái)分割

    public static void main(String[] args) {
        String str = "name=fly&age=20";
        String[] strings = str.split("&");//以字符&分割
        for (String s:strings) {
           // System.out.println(s);
            String[] ss = s.split("=");//分割之后再以=分割
            for (String tmp:ss) {
                System.out.println(tmp);
            }
        }
 
    }

?9.2多個(gè)分隔符分割

    public static void main(String[] args) {
        String str3 = "fly%12&age#hello";
        String[] ret = str3.split("%|&|#");//多個(gè)分隔符分割，用|隔開(kāi)
        for (String sss:ret) {
            System.out.println(sss);
        }
    }

?9.3特殊符號(hào)分割

1. 字符 "|","*","+" 都得加上轉(zhuǎn)義字符，前面加上 "\".
2. 而如果是 "" ，那么就得寫成 "\\".
3. 如果一個(gè)字符串中有多個(gè)分隔符，可以用 "|" 作為連字符 .

    public static void main(String[] args) {
        String str = "191.157.1.1";
        String[] result = str.split("\\.");
        for (String s:result) {
            System.out.println(s);
        }
 
        System.out.println("-------------");
        String str2 = "191\\157\\1\\1";
        String[] strings = str2.split("\\\\",3);//4是分為四組
        for (String ss:strings) {
            System.out.println(ss);
        }
 
        String str3 = "fly%12&age#hello";
        String[] ret = str3.split("%|&|#");//多個(gè)分隔符分割，用|隔開(kāi)
        for (String sss:ret) {
            System.out.println(sss);
        }
 
    }

10.提取子串str.substring(? )

    public static void main(String[] args) {
        String str = "abcdefg";
        String sub = str.substring(2,4);//提取子串,左閉右開(kāi)
        System.out.println(sub);
    }

?11.去空格

    public static void main(String[] args) {
        String str = "   abc  def   ";
        String ret = str.trim();//去除字符串左右兩邊的空格
        System.out.print(ret);
        System.out.println("---");
    }

12.字符串的拼接

    public static void main(String[] args) {
        String str = "abc";
        String ret = str.concat("fly");//字符串的拼接
        System.out.println(ret);
    }

13.StringBuffer ?

13.1字符串的拼接

    public static void main(String[] args) {
        String str = "hello";
        StringBuffer sb = new StringBuffer();
        sb.append(str);
        for (int i = 0; i < 10; i++) {
            sb.append(i);
            str = sb.toString();
        }
        System.out.println(str);
    }

13.2方法的返回類型

    public static StringBuffer func() {
        String str = "fly";
        return new StringBuffer(str);
    }
    public static void main(String[] args) {
        System.out.println(func());
    }