Java String substring() method returns the substring of this string. This method always returns a new string and the original string remains unchanged because .

Java String substring（）方法返回此字符串的子字符串。 此方法始终返回一个新字符串，而原始字符串则保持不变，因为 。

Java String substring（）方法 (Java String substring() Methods)

Java String substring method is overloaded and has two variants.

Java String子字符串方法已重载，并且具有两个变体。

1. substring(int beginIndex): This method returns a new string that is a substring of this string. The substring begins with the character at the specified index and extends to the end of this string.
   substring(int beginIndex) ：此方法返回一个新字符串，该字符串是该字符串的子字符串。 子字符串以指定索引处的字符开头，并延伸到该字符串的末尾。
2. substring(int beginIndex, int endIndex): The substring begins at the specified beginIndex and extends to the character at index endIndex – 1. Thus the length of the substring is (endIndex – beginIndex).
   substring(int beginIndex, int endIndex) ：子字符串从指定的beginIndex开始，并扩展到索引endIndex – 1处的字符。因此，子字符串的长度为（endIndex – beginIndex）。

String substring（）方法要点 (String substring() Method Important Points)

1. Both the string substring methods can throw IndexOutOfBoundsException if any of the below conditions met.
   • if the beginIndex is negative
   • endIndex is larger than the length of this String object
   • beginIndex is larger than endIndex
   如果满足以下任一条件，则这两个字符串子字符串方法都可以引发IndexOutOfBoundsException 。
   • 如果beginIndex为负
   • endIndex大于此String对象的长度
   • beginIndex大于endIndex
2. beginIndex is inclusive and endIndex is exclusive in both substring methods.
   在这两个子字符串方法中，beginIndex是包含的，endIndex是排除的。

Java String substring（）示例 (Java String substring() Example)

Here is a simple program for the substring in java.

这是Java中子字符串的简单程序。

package com.journaldev.util;public class StringSubstringExample {	public static void main(String[] args) {		String str = "www.journaldev.com";		System.out.println("Last 4 char String: " + str.substring(str.length() - 4));		System.out.println("First 4 char String: " + str.substring(0, 4));		System.out.println("website name: " + str.substring(4, 14));	}}

Output of the above substring example program is:

上面的子字符串示例程序的输出为：

Last 4 char String: .comFirst 4 char String: www.website name: journaldev

使用substring（）方法检查回文 (Checking Palindrome using substring() Method)

We can use the substring() method to check if a String is a palindrome or not.

我们可以使用substring（）方法来检查String是否是回文。

package com.journaldev.util;public class StringPalindromeTest {	public static void main(String[] args) {		System.out.println(checkPalindrome("abcba"));		System.out.println(checkPalindrome("XYyx"));		System.out.println(checkPalindrome("871232178"));		System.out.println(checkPalindrome("CCCCC"));	}	private static boolean checkPalindrome(String str) {		if (str == null)			return false;		if (str.length() <= 1) {			return true;		}		String first = str.substring(0, 1);		String last = str.substring(str.length() - 1);		if (!first.equals(last))			return false;		else			return checkPalindrome(str.substring(1, str.length() - 1));	}}

Here we are checking if the first letter and the last letter is the same or not. If they are not the same, return false. Otherwise, call the method again recursively passing the substring with the first and last letter removed.

在这里，我们检查第一个字母和最后一个字母是否相同。 如果它们不相同，则返回false。 否则，再次调用该方法以递归方式传递子字符串，并删除第一个和最后一个字母。

Reference:

参考：

翻译自: