Java 反转字符串的 10 种方法

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”。

1. 使用 + (String连接) 操作符

package net.javaguides.corejava.string;

/**

 * 

 * @author Ramesh Fadatare

 *

 */

public class ReverseWithStringConcat {

    public static void main(String[] args) {

        ReverseWithStringConcat concat = new ReverseWithStringConcat();

        concat.reverseWithStringConcat("javaguides");

    }

    private String reverseWithStringConcat(String input) {

        String output = new String();

        for (int i = (input.length() - 1); i >= 0; i--) {

            output += (input.charAt(i));

        }

        display(input, output);

        return output;

    }

    private void display(String input, String output) {

        System.out.println(" input string :: " + input);

        System.out.println(" output string :: " + output);

    }

}

输出:

input string :: javaguides

output string :: sediugavaj

2. 使用 StringBuilder

package net.javaguides.corejava.string;

/**

 * 

 * @author Ramesh Fadatare

 *

 */

public class ReverseWithStringBuilderBuiltinMethod {

    public static void main(String[] args) {

        ReverseWithStringBuilderBuiltinMethod builtinMethod = new ReverseWithStringBuilderBuiltinMethod();

        builtinMethod.reverseWithStringBuilderBuiltinMethod("javaguides");

    }

    public String reverseWithStringBuilderBuiltinMethod(String string) {

        final StringBuilder builder = new StringBuilder(string);

        display(string, builder.reverse().toString());

        return builder.reverse().toString();

    }

    private void display(String input, String output) {

        System.out.println(" input string :: " + input);

        System.out.println(" output string :: " + output);

    }

}

输出:对Java技术,架构技术感兴趣的同学,欢迎加Q君羊:625241190,一起学习,相互讨论。

input string :: javaguides

output string :: sediugavaj

3. 使用 String charAt 方法

package net.javaguides.corejava.string;

/**

 * 

 * @author Ramesh Fadatare

 *

 */

public class ReverseWithStringChatAt{

    public static void main(String[] args) {

        ReverseWithStringChatAt reverseWithStringBuilder = new ReverseWithStringChatAt();

        reverseWithStringBuilder.reverseWithStringBuilder("javaguides");

    }

    public String reverseWithStringChatAt(String string) {

        final StringBuilder builder = new StringBuilder();

        for (int i = (string.length() - 1); i >= 0; i--) {

            builder.append(string.charAt(i));

        }

        display(string, builder.toString());

        return builder.toString();

    }

    private void display(String input, String output) {

        System.out.println(" input string :: " + input);

        System.out.println(" output string :: " + output);

    }

}

输出:

input string :: javaguides

output string :: sediugavaj

4. 通过交换字符反转

package net.javaguides.corejava.string;

/**

 * 

 * @author Ramesh Fadatare

 *

 */

public class ReverseStringWithSwaps {

    public static void main(String[] args) {

        ReverseStringWithSwaps stringWithSwaps = new ReverseStringWithSwaps();

        stringWithSwaps.reverseWithSwaps("javaguides");

    }

    public String reverseWithSwaps(String string) {

        final char[] array = string.toCharArray();

        final int length = array.length - 1;

        final int half = (int) Math.floor(array.length / 2);

        char c;

        for (int i = length; i >= half; i--) {

            c = array[length - i];

            array[length - i] = array[i];

            array[i] = c;

        }

        display(string, String.valueOf(array));

        return String.valueOf(array);

    }

    private void display(String input, String output) {

        System.out.println(" input string :: " + input);

        System.out.println(" output string :: " + output);

    }

}

输出:

input string :: javaguides

output string :: sediugavaj

5. 使用 XOR(^) 操作符反转

package net.javaguides.corejava.string;

/**

 * 

 * @author Ramesh Fadatare

 *

 */

public class ReverseStringWithXOR {

    public static void main(String[] args) {

        ReverseStringWithXOR stringWithXOR = new ReverseStringWithXOR();

        stringWithXOR.reverseWithXOR("javaguides");

    }

    public String reverseWithXOR(String string) {

        final char[] array = string.toCharArray();

        final int length = array.length;

        final int half = (int) Math.floor(array.length / 2);

        for (int i = 0; i < half; i++) {

            array[i] ^= array[length - i - 1];

            array[length - i - 1] ^= array[i];

            array[i] ^= array[length - i - 1];

        }

        display(string, String.valueOf(array));

        return String.valueOf(array);

    }

    private void display(String input, String output) {

        System.out.println(" input string :: " + input);

        System.out.println(" output string :: " + output);

    }

}

输出:

input string :: javaguides

output string :: sediugavaj

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

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