Java中几个字符串的操作函数总结

清疚 2023-07-14 14:00 14阅读 0赞

**1. String.replace()**

**功能：以新字符串（或单个字符）替换旧的字符串（或单个字符）**

**用法：**

**举例：**

class Solution {
        public static void main(String []args){
        	String str="abbcd";
        	System.out.println("原字符串"+str);
        	String str2=str.replace('b', '#');
        	System.out.println("替换后的字符串"+str2);
        }
    }
    输出：
    原字符串abbcd
    替换后的字符串a##cd
    
    
    
    class Solution{
        public static void main(String []args){
        	String str="abbcd";
        	System.out.println("原字符串"+str);
        	String str2=str.replace("bb", "$$");
        	System.out.println("替换后的字符串"+str2);
        }
    }
    输出：
    原字符串abbcd
    替换后的字符串a$$cd

**源码：**

public String replace(CharSequence target, CharSequence replacement) {
            return Pattern.compile(target.toString(), Pattern.LITERAL).matcher(
                    this).replaceAll(Matcher.quoteReplacement(replacement.toString()));
        }

**2.String.replaceAll()**

**功能：用正则表达式的方法替换原字符串**

**用法：**

**举例：**

class Solution {
        public static void main(String []args){
        	String str="abbcbd";
        	System.out.println("原字符串"+str);
        	String str2=str.replaceAll("b+","#");//匹配一个及以上b字符序列
        	System.out.println("替换后的字符串"+str2);
        }
    }
    输出：
    原字符串abbcbd
    替换后的字符串a#c#d

**源码：**

public String replaceAll(String regex, String replacement) {
            return Pattern.compile(regex).matcher(this).replaceAll(replacement);
        }
    
        /**
         * Replaces each substring of this string that matches the literal target
         * sequence with the specified literal replacement sequence. The
         * replacement proceeds from the beginning of the string to the end, for
         * example, replacing "aa" with "b" in the string "aaa" will result in
         * "ba" rather than "ab".

**3.String.split()**

**功能：**Java中的 split  函数是用于按指定字符（串）或正则去分割某个字符串，结果以字符串数组形式返回；

**用法：**最常用的一种用法，传参为字符串或正则表达式，[点击到达参考文章][Link 1]

**举例：**

String str="1234@abc";
    String[] a = str.split("@");
    System.out.println("处理结果: "+a[0]+","+a[1]);   //输出的是: 处理结果: 1234,abc

**源码：**

public String[] split(String regex) {
            return split(regex, 0);
        }
    
        /**
         * Returns a new String composed of copies of the
         * {@code CharSequence elements} joined together with a copy of
         * the specified {@code delimiter}.

**4.String.trim()**

**功能：**trim() 方法用于删除字符串的头尾空白符。

**用法：**来自菜鸟教程

**举例：**

public class Test {
        public static void main(String args[]) {
            String Str = new String("    www.runoob.com    ");
            System.out.print("原始值 :" );
            System.out.println( Str );
    
            System.out.print("删除头尾空白 :" );
            System.out.println( Str.trim() );
        }
    }

**源码：**

* @return  A string whose value is this string, with any leading and trailing white
         *          space removed, or this string if it has no leading or
         *          trailing white space.
         */
        public String trim() {
            int len = value.length;
            int st = 0;
            char[] val = value;    /* avoid getfield opcode */
    
            while ((st < len) && (val[st] <= ' ')) {
                st++;
            }
            while ((st < len) && (val[len - 1] <= ' ')) {
                len--;
            }
            return ((st > 0) || (len < value.length)) ? substring(st, len) : this;
        }

**5.StringBuilder.append()**

**功能：**在StringBuilder类型的可变长字符串对象后添加字符串（或其他对象）

**用法：**

**举例：**

class Solution {
        public static void main(String []args){
        	StringBuilder str=new StringBuilder("");
        	System.out.println("加入字符串: "+str.append("我是新加入的"));
        	System.out.println("加入基本类型: "+str.append(134));
        }
    }
    输出：
    加入字符串: 我是新加入的
    加入基本类型: 我是新加入的134

**源码：**

@Override
        public StringBuilder append(Object obj) {
            return append(String.valueOf(obj));
        }
    
        @Override
        public StringBuilder append(String str) {
            super.append(str);
            return this;
        }
    
        /**
         * Appends the specified {@code StringBuffer} to this sequence.

[Link 1]: https://blog.csdn.net/shenzhenNBA/article/details/8086110?depth_1-utm_source=distribute.pc_relevant.none-task&utm_source=distribute.pc_relevant.none-task