public static void main(String[] args) {String str = "abcdef";char ch = str.charAt(2);System.out.println(ch);//输出:c}
compareTo
compareToIgnoreCase
public static void main(String[] args) {String str1 = "abcdef";int ret1 = str1.compareTo("abcee");System.out.println(ret1);//输出-1int ret2 = str1.compareToIgnoreCase("AbcDe");System.out.println(ret2);//输出1}
关于返回值:
- 返回0表示两个字符串的值相同。
- 如果不相同,返回两个字符串 的 第一位不相同字符 的 ASCII之差。
- 如果是包含关系的话,返回长度之差。
public static void main(String[] args) {String str = "abcdef";boolean bool1 = str.contains("abc");boolean bool2 = str.contains("aaa");System.out.println(bool1);//输出trueSystem.out.println(bool2);//输出false}
public static void main(String[] args) {String str = "abcdef";boolean bool1 = str.equals("abcdef");boolean bool2 = str.equals("aaa");System.out.println(bool1);//输出trueSystem.out.println(bool2);//输出falseString str2 = "abcdef";boolean bool3 = str.equalsIgnoreCase("Abcdef");System.out.println(bool3);//输出true}
注意:比较两个字符串内容是否相等使用“==”是在比较引用对象存储的地址。
indexOf
public static void main(String[] args) {String str = "abcdef";int ret = str.indexOf("cdef");System.out.println(ret);//输出2int ret2 = str.lastIndexOf("cde");System.out.println(ret2);//输出2}
public static void main(String[] args) {String str1 = "abcdef";boolean bool1 = str1.isEmpty();String str2 = "";boolean bool2 = str2.isEmpty();System.out.println(bool1);//输出falseSystem.out.println(bool2);//输出true}
public static void main(String[] args) {String str = "abcdef";System.out.println(str.length());//输出6}
注意与属性的length区分,求字符串长度要加(),数组则不用!
replace
replaceFrist
public static void main(String[] args) {String str1 = "Hi do you like learning English?";String str2 = str1.replace(' ','/');System.out.println(str2);//输出Hi/do/you/like/learning/English?String str3 = str1.replaceFirst(" ",",");System.out.println(str3);//输出Hi,do you like learning English?String str4 = str1.replaceAll(" ","//");//替换字符串,类似replace替换字符!System.out.println(str4);//输出Hi//do//you//like//learning//English?}
public static void main(String[] args) {String str1 = "Hi do you like learning English?";String[] str2 = str1.split(" ");for (String x:str2) {System.out.println(x);/*输出 HidoyoulikelearningEnglish?*/}}
public static void main(String[] args) {String str1 = "abcdef";String str2 = str1.substring(1,3);System.out.println(str2);//输出bc}
public static void main(String[] args) {String str1 = "abcdef";char[] str2 = str1.toCharArray();for (char ch:str2) {System.out.print(ch+" ");//输出a b c d e f}}
toUpperCase
public static void main(String[] args) {String str1 = "abcdef";String str2 = str1.toUpperCase();System.out.println(str2);//输出ABCDEFString str3 = str2.toLowerCase();System.out.println(str3);//输出abcdef}
public static void main(String[] args) {String str1 = " Hi do you like learning English? ";String str2 = str1.trim();System.out.println(str1);//输出 Hi do you like learning English?System.out.println(str2);//输出Hi do you like learning English?}
public static void main(String[] args) {String s = String.format("%d-%d-%d", 2019, 9,14);System.out.println(s);//输出2019-9-14}
class Student {int id;String name;public Student(int id, String name) {this.id = id;this.name = name;}@Overridepublic String toString() { //重写toStrong便于我们打印return "Student{" +"id=" + id +", name='" + name + '\'' +'}';}
}public class text2 {public static void main(String[] args) {Student student = new Student(10,"zhangsan");String str = String.valueOf(student);System.out.println(str);//输出Student{id=10, name='zhangsan'}}
}
使用StringBuilder需要导入包:import java.lang.StringBuilder;
public static void main(String[] args) {StringBuilder strbu1 = new StringBuilder("abcdef");strbu1.reverse();System.out.println(strbu1);//输出fedcba}
public static void main(String[] args) {StringBuilder strbu1 = new StringBuilder("abcdef");strbu1.append('g');System.out.println(strbu1);//输出abcdefg}
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