在这篇文章中,我们会讨论10种用Java反转字符串的方法,通过10个Java程序反转字符串。例如,把字符串“javaguides” 反转为 “sediugavaj”。以下将介绍剩下的5种方法。
6. 使用堆栈
package net.javaguides.corejava.string;
import java.util.Stack;
/**
*
* @author Ramesh Fadatare
*
*/
public class ReverseStringUsingStack {
// Function to reverse a string in Java using a stack and character array
public static String reverse(String str) {
// base case: if string is null or empty
if (str == null || str.equals(""))
return str;
// create an empty stack of characters
Stack < Character > stack = new Stack < Character > ();
// push every character of the given string into the stack
char[] ch = str.toCharArray();
for (int i = 0; i < str.length(); i++)
stack.push(ch[i]);
// start from index 0
int k = 0;
// pop characters from the stack until it is empty
while (!stack.isEmpty()) {
// assign each popped character back to the character array
ch[k++] = stack.pop();
}
// convert the character array into string and return it
return String.copyValueOf(ch);
}
public static void main(String[] args) {
String str = "javaguides";
str = reverse(str); // string is immutable
System.out.println("Reverse of the given string is : " + str);
}
}
输出:
Reverse of the given string is : sediugavaj
7. 使用 Collections reverse() 方法
package net.javaguides.corejava.string;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
/**
*
* @author Ramesh Fadatare
*
*/
public class ReverseStringUsingCollectionsReverseMethod {
// Function to reverse a string in Java using Collections.reverse()
public static String reverse(String str) {
// base case: if string is null or empty
if (str == null || str.equals(""))
return str;
// create an empty list of characters
List < Character > list = new ArrayList < Character > ();
// push every character of the given string into it
for (char c: str.toCharArray())
list.add(c);
// reverse list using java.util.Collections reverse()
Collections.reverse(list);
// covert ArrayList into String using StringBuilder and return it
StringBuilder builder = new StringBuilder(list.size());
for (Character c: list)
builder.append(c);
return builder.toString();
}
public static void main(String[] args) {
String str = "Java Guides";
// String is immutable
str = reverse(str);
System.out.println("Reverse of the given string is : " + str);
}
}
输出:
Reverse of the given string is : sediuG avaJ
8. 使用 Byte 数组
package net.javaguides.corejava.string;
/**
*
* @author Ramesh Fadatare
*
*/
public class ReverseStringUsingByteArray {
// Function to reverse a string in Java using byte array
public static String reverse(String str) {
// return if string is null or empty
if (str == null || str.equals(""))
return str;
// convert string into bytes
byte[] bytes = str.getBytes();
// start from the two end points l and h of the given string
// and increment l & decrement h at each iteration of the loop
// until two end-points intersect (l >= h)
for (int l = 0, h = str.length() - 1; l < h; l++, h--) {
// Swap values at l and h
byte temp = bytes[l];
bytes[l] = bytes[h];
bytes[h] = temp;
}
// convert byte array back into the string
return new String(bytes);
}
public static void main(String[] args) {
String str = "Java Guides";
// String is immutable
str = reverse(str);
System.out.println("Reverse of the given string is : " + str);
}
}
输出:
Reverse of the given string is : sediuG avaJ
9. 使用 substring() 方法
package net.javaguides.corejava.string;
/**
*
* @author Ramesh Fadatare
*
*/
public class UsingSubStringFunction {
// Function to reverse a string in Java using recursion
private static String reverse(String str) {
// base case: if string is null or empty
if (str == null || str.equals(""))
return str;
// last character + recurse for remaining string
return str.charAt(str.length() - 1) + reverse(str.substring(0, str.length() - 1));
}
public static void main(String[] args) {
String str = "javaguides";
// string is immutable
str = reverse(str);
System.out.println("Reverse of the given string is : " + str);
}
}
输出:
Reverse of the given string is : sediugavaj
10. 使用递归
package net.javaguides.corejava.string;
/**
*
* @author Ramesh Fadatare
*
*/
public class UsingRecursion {
static int i = 0;
// Recursive function to reverse a string in Java using static variable
private static void reverse(char[] str, int k) {
// if we have reached the end of the string
if (k == str.length)
return;
// recurse for next character
reverse(str, k + 1);
if (i <= k) {
char temp = str[k];
str[k] = str[i];
str[i++] = temp;
}
}
public static String reverse(String str) {
// base case: if string is null or empty
if (str == null || str.equals(""))
return str;
// convert string into a character array
char[] A = str.toCharArray();
// reverse character array
reverse(A, 0);
// convert character array into the string
return String.copyValueOf(A);
}
public static void main(String[] args) {
String str = "Java Guides";
// string is immutable
str = reverse(str);
System.out.println("Reverse of the given string is : " + str);
}
}
输出:
Reverse of the given string is : sediuG avaJ