java——基础数据类型—

java——基础数据类型——字符串操作

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获取字符串长度

String st = "bacdeg";

System.out.println(st.length());

System.out.println("bacdeg".length());

执行结果：

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判断字符串中是否包含有某个字符

String s7 = "ageheafeRTEYEWRTEWEWYWEHEhehaheh";

System.out.println(s7.length());

System.out.println(s7.contains("a"));

System.out.println("ageheafeRTEYEWRTEWEWYWEHEhehaheh".contains("a"));

System.out.println(s7.contains("aT"));

System.out.println("ageheafeRTEYEWRTEWEWYWEHEhehaheh".contains("aT"));

执行结果：

true

false

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将字符串全部变为小写或者大写

String s7 = "ageheafeRTEYEWRTEWEWYWEHEhehaheh";

System.out.println(s7.toLowerCase()); ——全部变为小写

System.out.println(s7.toUpperCase()); ——全部变为大写

执行结果：

ageheaferteyewrtewewywehehehaheh

AGEHEAFERTEYEWRTEWEWYWEHEHEHAHEH

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判断字符串是否以某个（串）字符开头或者结尾

String s7 = "ageheafeRTEYEWRTEWEWYWEHEhehaheh";

System.out.println(s7.startsWith("age"));

System.out.println(s7.startsWith("ageG"));

System.out.println(s7.endsWith("heh"));

System.out.println(s7.endsWith("heha"));

执行结果：

true

false

true

false

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判断两串字符串是否完全相等

String s7 = "ageheafeRTEYEWRTEWEWYWEHEhehaheh";

System.out.println(s7.equals("ageheaferteyewrtewewywehehehaheh"));

System.out.println(s7.equals("AGEHEAFERTEYEWRTEWEWYWEHEHEHAHEH"));

System.out.println(s7.equals("ageheafeRTEYEWRTEWEWYWEHEhehaheh"));

System.out.println(s7.equals("ageheafeRTEYEWRTEWEWYWEHEhehaheh "));

执行结果：

false

true

false

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忽略大小写，判断两串字符串是否完全相等

String s7 = "ageheafeRTEYEWRTEWEWYWEHEhehaheh";

System.out.println(s7.equalsIgnoreCase("ageheaferteyewrtewewywehehehaheh"));

System.out.println(s7.equalsIgnoreCase("AGEHEAFERTEYEWRTEWEWYWEHEHEHAHEH"));

System.out.println(s7.equalsIgnoreCase("ageheafeRTEYEWRTEWEWYWEHEhehaheh"));

System.out.println(s7.equalsIgnoreCase("ageheafeRTEYEWRTEWEWYWEHEhehaheh "));

执行结果：

true

false

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替换字符为目标字符

str.replace(char oldChar , char newChar )

——oldChar：要替换的字符或者字符串；

——newChar：用于替换原来的字符串的内容；

String s15 = " a g eheafe54RTEYEWRTrh rhr EagW EWYWEH Ehehah eh ";

System.out.println(s15.replace("a","999"));

System.out.println(s15);

执行结果：

999 g ehe999fe54RTEYEWRTrh rhr E999gW EWYWEH Eheh999h eh

a g eheafe54RTEYEWRTrh rhr EagW EWYWEH Ehehah eh

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去除字符串开头和结尾的空格

String s14 = " a g eheafe54RTEYEWRTrh rhr EagW EWYWEH Ehehah eh ";

System.out.println(s14.length());

System.out.println(s14.trim());

System.out.println(s14.trim().length());

执行结果：

a g eheafe54RTEYEWRTrh rhr EagW EWYWEH Ehehah eh

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indexOf()方法返回的是搜索的字符或者字符串首次出现的位置

lastIdexOf()方法返回的是搜索的字符或者字符串最后一次出现的位置

PS：字符串的下标识是： -1——length（）-1

PS：如果没有检索到字符串S，则返回-1

String s8 = "ageheafe54RTEYEWRTrhrhrEagWEWYWEHEhehaheh";

String s9 = " ageheafe54RTEYEWRTrhrhrEagWEWYWEHEhehaheh";

String s10 = "ageheafe54RTEYEWRTrhrhrEagWEWYWEHEhehaheh ";

String s11 = " ageheafe54RTEYEWRTrhrhrEagWEWYWEHEhehaheh ";

String s12 = " ageheafe54RTEYEWRTrh rhrEagWEWYWEHEhehaheh ";

System.out.println(s8.length()); ——41

System.out.println(s9.length()); ——42

System.out.println(s10.length()); ——42

System.out.println(s11.length()); ——43

System.out.println(s12.length()); ——44

System.out.println(s8.indexOf("a"));——————0

System.out.println(s8.indexOf("e"));——————2

System.out.println(s9.indexOf("a"));——————1

System.out.println(s9.indexOf("e"));——————3

System.out.println(s9.indexOf(" "));——————0

System.out.println(s9.indexOf("z"));—————— -1

System.out.println(s9.lastIndexOf("a"));——————38

System.out.println(s9.lastIndexOf("h"));——————41

System.out.println(s9.lastIndexOf(" "));——————0

System.out.println(s9.lastIndexOf("z"));—————— -1

System.out.println(s9.lastIndexOf(""));——————42

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获取指定索引位置的字符

String s9 = " ageheafe54RTEYEWRTrhrhrEagWEWYWEHEhehaheh";

System.out.println(s9.charAt(0));

System.out.println(s9.charAt(1));

执行结果：

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获取子字符串——利用下标进行截取，注意下标是从0开始的，空格占用一个索引位置

（1）、substring(int beginIndex)——从指定的索引位置开始截取，直到字符串的结尾；

（1）、substring(int beginIndex,int endIndex)——从指定的索引位置开始截取，到指定索引结束；

String s13 = " a g eheafe54RTEYEWRTrh rhr EagW EWYWEH Ehehah eh ";

System.out.println(s13.substring(2));

System.out.println(s13.substring(2,29));

执行结果：

g eheafe54RTEYEWRTrh rhr EagW EWYWEH Ehehah eh

g eheafe54RTEYEWRTrh rhr

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字符串分隔

（1）、split( String sign)：根据给定的分隔符号对字符串进行分隔；

sign为分隔符号，如果想定义多个分隔符号，可以使用符号“|”，例如“,|=”，表示分隔符号分别为，和 = ；

（2）、split(String sign,int limit)：根据给定的分隔符对字符串进行拆分，并限定拆分次数；

sign为分隔符号，如果想定义多个分隔符号，可以使用符号“|”，例如“,|=”，表示分隔符号分别为，和 = ；

limit：模式匹配次数，如果设置为n，则分割为n-1次，得到的数组长度不会大于n，数组的最后一项，是最后匹配的分隔符以后的全部内容；

String s16 = "1,2,333,444,55,6664,75775,8y43u";

String[] firstArray = s16.split(",");

System.out.println(firstArray.length);

System.out.println("----------------");

System.out.println(firstArray[0]);

System.out.println(firstArray[1]);

System.out.println(firstArray[2]);

System.out.println("----------------");

for(String p : firstArray)

{

System.out.println(p);

}

执行结果：

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333

----------------

333

444

6664

75775

8y43u

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String s21 = "1,2=333,444=55,6664,75775,8y43u";

String[] firstArray8 = s21.split(",|=");

System.out.println(firstArray8.length);

System.out.println("----------------");

System.out.println(firstArray8[0]);

System.out.println(firstArray8[1]);

System.out.println(firstArray8[2]);

System.out.println("----------------");

for(String p : firstArray8)

{

System.out.println(p);

}

执行结果：

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333

----------------

333

444

6664

75775

8y43u

String s20 = "1,2,333,444,55,6664,75775,8y43u";

String[] firstArray7 = s20.split(",",4);

System.out.println(firstArray7.length);

System.out.println("----------------");

System.out.println(firstArray7[0]);

System.out.println(firstArray7[1]);

System.out.println(firstArray7[2]);

System.out.println("----------------");

for(String p : firstArray7)

{

System.out.println(p);

}

执行结果：

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333

----------------

333

444,55,6664,75775,8y43u

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