在 Java 中迭代字符串的字符

给定长度为N 的字符串str ，任务是遍历字符串并打印给定字符串的所有字符。

方法 1：朴素的方法

解决这个问题的最简单的方法是迭代的范围内的环[0，N - 1] ，其中Ñ表示字符串的长度，使用该可变我并打印的值STR [1] 。

// Java Program to Iterate Over the Characters of a String
// Using Naive Approach

// Importing classes from respective packages
import java.io.*;
import java.util.*;

// Main class
class GFG {

	// Method 1
	// Function to traverse the string and
	// print the characters of the string
	static void traverseString(String str)
	{
		// Traverse the string
		for (int i = 0; i < str.length(); i++) {

			// Print current character
			System.out.print(str.charAt(i) + " ");
		}
	}

	// Method 2
	// Main driver method
	public static void main(String[] args)
	{
		// Custom input string
		String str = "GeeksforGeeks";

		// Calling the Method 1
		traverseString(str);
	}
}

方法 2：使用String.toCharArray()方法

在这种方法中，我们使用String.toCharArray()方法将字符串转换为字符数组。然后使用 for 循环或 for-each 循环迭代字符数组。

// Java Program to Iterate Over the Characters of a String
// Using String.toCharArray() method

// Importing classes from respective packages
import java.io.*;
import java.util.*;

// Main class
class GFG {

	// Method 1
	// To traverse the string and
	// print the characters of the string
	static void traverseString(String str)
	{
		char[] ch = str.toCharArray();

		// Traverse the character array
		for (int i = 0; i < ch.length; i++) {

			// Print current character
			System.out.print(ch[i] + " ");
		}
	}

	// Method 2
	// Main driver method
	public static void main(String[] args)
	{
		// Custom input string
		String str = "GeeksforGeeks";

		// Calling the Method 1
		traverseString(str);
	}
}

方法 3：使用 CharacterIterator

在这种方法中，我们使用 CharacterIterator 方法current()获取当前字符和next()向前移动一个位置。StringCharacterIterator 提供了 CharacterIterator 的实现。

// Java Program to Iterate Over the Characters of a String
// Using CharacterIterator

// Importing required libraries
import java.io.*;
import java.text.*;

// Main class
class GFG {

	// Method 1
	// To traverse the string and
	// print the characters of the string
	static void traverseString(String str)
	{
		CharacterIterator it
			= new StringCharacterIterator(str);

		// Iterate and print current character
		while (it.current() != CharacterIterator.DONE) {
			System.out.print(it.current() + " ");

			// Moving onot next element in the object
			// using next() method
			it.next();
		}
	}

	// Method 2
	// Main driver method
	public static void main(String[] args)
	{
		// Custom input string
		String str = "GeeksforGeeks";

		// Calling the Method 1
		traverseString(str);
	}
}

方法 4：使用 StringTokenizer

在这种方法中，我们使用Java 中的StringTokenizer类。它根据分隔符将字符串分解为标记。它的用法是气馁。

// Java Program to Iterate Over the Characters of a String
// Using StringTokenizer

// Importing required librares
import java.io.*;
import java.util.*;

// Main class
class GFG {

	// Method 1
	// To traverse the string and
	// print the characters of the string
	static void traverseString(String str)
	{
		// If returnDelims is true, use the string itself as
		// a delimiter
		StringTokenizer st
			= new StringTokenizer(str, str, true);

		while (st.hasMoreTokens()) {
			System.out.print(st.nextToken() + " ");
		}

		System.out.println();

		// If returnDelims is false, use an empty string as
		// a delimiter
		st = new StringTokenizer(str, "", false);

		while (st.hasMoreTokens()) {
			System.out.print(st.nextToken() + " ");
		}
	}

	// Method 2
	// Main driver method
	public static void main(String[] args)
	{
		// Custom input string
		String str = "GeeksforGeeks";

		/// Calling the above Method1
		traverseString(str);
	}
}

方法 5：使用 String.split() 方法

在这种方法中，我们使用String 类的split()方法。它根据提供的正则表达式将字符串拆分为子字符串。

// Java Program to Iterate Over the Characters of a String
// Using String.split() method

// Importing required classes from respective packages
import java.io.*;
import java.util.*;

// Main class
class GFG {

	// Method 1
	// To traverse the string and
	// print the characters of the string
	static void traverseString(String str)
	{
		// Split str around matches of empty string ""
		String[] substrings = str.split("");
		
	for (String ch : substrings) {
			System.out.print(ch + " ");
		}
	}
	
	// Method 2
	// main driver method
	public static void main(String[] args)
	{
		// Custom input string
		String str = "GeeksforGeeks";

		// Calling the Method1 to
		// print the characters of the string
		traverseString(str);
	}
}

方法六：使用番石榴库

在这种方法中，我们使用Lists.charactersOf(str)方法，该方法返回不可变字符列表的视图。

// Java Program to Iterate Over the Characters of a String
// Using Guava Library

// Importing required classes from respective packages
import com.google.common.collect.Lists;
import java.io.*;

// Main class
class GFG {

	// Method 1
	// To traverse the string and
	// print the characters of the string
	static void traverseString(String str)
	{
		// Using enhanced for loop
		for (Character ch : Lists.charactersOf(str)) {
			System.out.print(ch + " ");
		}

		// A new line is required
		System.out.println();

		// Using listIterator on the List
		// List<Characters>
		// iterator()
		// lambda
		Lists.charactersOf(str)
			.listIterator()
			.forEachRemaining(
				ch -> System.out.print(ch + " "));

		// A new line is required
		System.out.println();

		// Using method reference with listIterator
		// List<Characters>
		// iterator()
		Lists.charactersOf(str)
			.listIterator()
			.forEachRemaining(System.out::print);
	}
	
	// Method 2
	// Main driver method
	public static void main(String[] args)
	{
		// Custom input string
		String str = "GeeksforGeeks";

		// Calling the Method1 to
		// print the characters of the string
		traverseString(str);
	}
}

方法 7：使用 String.chars() 方法

在这种方法中，我们使用String 类的chars()方法。由于性能原因，此方法不返回 Stream<Character> 对象。它返回一个IntStream（整数流）对象，该对象可以转换为 Stream<Character>（字符流）。

// Java Program to Iterate Over the Characters of a String
// Using String.chars() method

// Importing classes from required packages
import com.google.common.collect.Lists;
import java.io.*;

// main class
class GFG {

	// Method 1
	// to traverse the string and
	// print the characters of the string
	static void traverseString(String str)
	{
		// Display message for better readibility
		System.out.println(
			"Auto boxing into Stream<Character>");

		// Using method reference
		str.chars()
			.mapToObj(Character::toChars)
			.forEach(System.out::print);

		str.chars().forEach(System.out::print);

		// A new line is required
		System.out.println();

		// Using lambda expressions by casting int to char
		str.chars()
			.mapToObj(i -> Character.valueOf((char)i))
			.forEach(System.out::print);

		// A new line is required
		System.out.println();

		str.chars()
			.mapToObj(i -> (char)i)
			.forEach(System.out::print);

		// A new line is required
		System.out.println();
		str.chars()
			.mapToObj(
				i -> new StringBuilder().appendCodePoint(i))
			.forEach(System.out::print);

		// A new line is required
		System.out.println();

		// Display message for better readibility
		System.out.println(
			"Without boxing into Stream<Character>");

		str.chars().forEach(
			i -> System.out.print(Character.toChars(i)));

		// A new line is required
		System.out.println();

		str.chars().forEach(i -> System.out.print((char)i));

		// A new line is required for
		// readibilty in output clearly
		System.out.println();

		str.chars().forEach(
			i
			-> System.out.print(
				new StringBuilder().appendCodePoint(i)));
	}

	// Method 2
	// main driver method
	public static void main(String[] args)
	{
		// Custom input string
		String str = "GeeksforGeeks";

		// Calling the Method 1 to
		// print the characters of the string
		traverseString(str);
	}
}

方法 8：使用代码点

在这种方法中，我们使用String.codePoints()方法返回一个 Unicode 值流。

// Java Program to Iterate Over the Characters of a String
// Using Code Points

// importing classes from respective packages
import com.google.common.collect.Lists;
import java.io.*;

// main class
class GFG {

	// Method 1
	// To traverse the string and
	// print the characters of the string
	static void traverseString(String str)
	{
		// Display message for better readibility
		System.out.println(
			"Auto boxing into Stream<Character>");
		
		// Using method reference
		str.codePoints()
			.mapToObj(Character::toChars)
			.forEach(System.out::print);
		str.codePoints().forEach(System.out::print);
		
		// New kine is required
		System.out.println();
		
		// Using lambda expressions by casting int to char
		str.codePoints()
			.mapToObj(i -> Character.valueOf((char)i))
			.forEach(System.out::print);

		// New line is required
		System.out.println();

		// now using the codepoints() over the string
		str.codePoints()
			.mapToObj(i -> (char)i)
			.forEach(System.out::print);

		// New line is required
		System.out.println();
		
		str.codePoints()
			.mapToObj(
				i -> new StringBuilder().appendCodePoint(i))
			.forEach(System.out::print);

		
		System.out.println();
		
	// Display message for readibilty in output
	System.out.println(
			"Without boxing into Stream<Character>");
		str.codePoints().forEach(
			i -> System.out.print(Character.toChars(i)));

		System.out.println();
		
	str.codePoints().forEach(
			i -> System.out.print((char)i));

		System.out.println();
		
	str.codePoints().forEach(
			i
			-> System.out.print(
				new StringBuilder().appendCodePoint(i)));
	}
	
	// Method 2
	// main driver method
	public static void main(String[] args)
	{
		// Custom input string
		String str = "GeeksforGeeks";

	// Calling the Method1 to
	// print the characters of the string
		traverseString(str);
	}
}