Java字符串replace()，replaceFirst()和replaceAll()方法
该replace()方法
String类的replace()方法接受两个String值-
一个表示要替换的String（子字符串）部分。
另一个代表需要替换指定子字符串的字符串。
使用此方法，您可以替换java中字符串的一部分。
示例
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class ReplaceExample {
public static void main(String args[]) throws FileNotFoundException {
String filePath = "D://input.txt";
Scanner sc = new Scanner(new File(filePath));
StringBuffer sb = new StringBuffer();
String input;
while (sc.hasNextLine()) {
input = sc.nextLine();
sb.append(input);
}
String contents = sb.toString();
System.out.println("Contents of the file: \n"+contents);
System.out.println(" ");
//用所需的单词替换单词
contents = contents.replace("Nhooo", "TP");
System.out.println("Contents of the file after replacing the desired word: \n"+contents);
}
}输出结果
Contents of the file: Hello how are you welcome to Nhooo. At Nhooo provide hundreds of technical tutorials for free. Contents of the file after replacing the desired word: Hello how are you welcome to TP. At TP provide hundreds of technical tutorials for free.
此方法的另一种变体还接受两个字符，分别代表现有字符和一个字符（以相同顺序），并在整个字符串中用新字符替换旧字符。
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class ReplaceExample {
public static void main(String args[]) throws FileNotFoundException {
String filePath = "D://input.txt";
Scanner sc = new Scanner(new File(filePath));
StringBuffer sb = new StringBuffer();
String input;
while (sc.hasNextLine()) {
input = sc.nextLine();
sb.append(input);
}
String contents = sb.toString();
System.out.println("Contents of the file: \n"+contents);
System.out.println(" ");
//用所需的单词替换单词
contents = contents.replace('T', '#');
System.out.println("Contents of the file after replacing the desired word: \n"+contents);
}
}输出结果
Contents of the file: Hello how are you welcome to Nhooo. At Nhooo provide hundreds of technical tutorials for free. Contents of the file after replacing the desired word: Hello how are you welcome to #utorialspoint. At #utorialspoint provide hundreds of technical tutorials for free.
该replaceAll()方法
String类的replaceAll()方法接受两个表示正则表达式的字符串和一个替换模式/字符串，并用指定的模式/字符串替换匹配的值。
示例
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class replaceAllExample {
public static void main(String args[]) throws FileNotFoundException {
String filePath = "D://input.txt";
Scanner sc = new Scanner(new File(filePath));
StringBuffer sb = new StringBuffer();
String input;
while (sc.hasNextLine()) {
input = sc.nextLine();
sb.append(input);
}
String contents = sb.toString();
System.out.println("Contents of the file: \n"+contents);
System.out.println();
//用所需的单词替换单词
contents = contents.replaceAll("\\bNhooo\\b", "TP");
System.out.println("Contents of the file after replacing the desired word: \n"+contents);
}
}输出结果
Contents of the file: Hello how are you welcome to Nhooo. At Nhooo provide hundreds of technical tutorials for free. Contents of the file after replacing the desired word: Hello how are you welcome to TP. At TP provide hundreds of technical tutorials for free.
该replaceFirst()方法
String类（也可以是replace类）的replaceFirst()方法接受两个表示正则表达式的字符串和一个替换字符串，然后用替换字符串替换第一个匹配项。
示例
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class ReplaceExample {
public static void main(String args[]) throws FileNotFoundException {
String filePath = "D://input.txt";
Scanner sc = new Scanner(new File(filePath));
StringBuffer sb = new StringBuffer();
String input;
while (sc.hasNextLine()) {
input = sc.nextLine();
sb.append(input);
}
String contents = sb.toString();
System.out.println("Contents of the file: \n"+contents);
System.out.println(" ");
//用所需的单词替换单词
contents = contents.replaceFirst("Nhooo", "TP");
System.out.println("Contents of the file after replacing the desired word: \n"+contents);
}
}输出结果
Contents of the file: Hello how are you welcome to Nhooo. At Nhooo provide hundreds of technical tutorials for free. Contents of the file after replacing the desired word: Hello how are you welcome to TP. At Nhooo provide hundreds of technical tutorials for free.
注意-所有这些方法都区分大小写。