java-string

1、String

1.1 代码

package com.nash.java.pop.ch05_string;

/**
 * 字符串 String
 * 1、值不可变、引用可变
 */
public class StringApp {

    public static void main(String[] args){
        // 1) 字符串定义
        String str = "hello world hello new world ";
        String str2 = "hello java ";
        String str3 = "hello world ";

        // 2) 字符串操作
        // 返回指定位置的字符
        System.out.println("charAt():\t " + str.charAt(0));
        // 返回指定位置的字符的Unicode编码
        System.out.println("codePointAt():\t " + str.codePointAt(0));
        // 拼接字符串
        System.out.println("concat():\t " + str.concat(str2));
        System.out.println("+:\t " + str+str2);
        // 是否包含某子串
        System.out.println("contains():\t " + str.contains("hello"));
        // 比较字符串对象(内存地址)
        System.out.println("equals():\t " + str.equals(str2));
        // 比较字符串内容
        System.out.println("equalsIgnoreCase():\t " + str.equalsIgnoreCase(str3));
        // 获取hashCode
        System.out.println("hashCode():\t " + str.hashCode());
        // 返回某子串首次出现的位置
        System.out.println("indexOf():\t " + str.indexOf("world"));
        // 返回字符串长度
        System.out.println("length():\t " + str.length());
        // 正则匹配
        System.out.println("matches():\t " + str.matches("^hello.*"));
        // 替换
        System.out.println("replace():\t " + str.replace("hello","replaced"));
        System.out.println("replaceAll():\t " + str.replaceAll("hello","replaced"));
        // 切割（指定分隔符）
        String[] splits = str.split(" ");
        for (String split:splits){
            System.out.println("split():\t " + split);
        }
        // 拼接（指定分隔符）
        System.out.println("join():\t " + String.join("--",str,str2));
        // 子串
        System.out.println("substring():\t " + str.substring(6));
        // 大写
        System.out.println("toUpperCase():\t " + str.toUpperCase());
        // 去除头尾空格
        System.out.println("trim():\t " + str.trim());

    }
}

1.2 结果

charAt():    h
codePointAt():   104
concat():    hello world hello new world hello java 
+:   hello world hello new world hello java 
contains():  true
equals():    false
equalsIgnoreCase():  false
hashCode():  1881745208
indexOf():   6
length():    28
matches():   true
replace():   replaced world replaced new world 
replaceAll():    replaced world replaced new world 
split():     hello
split():     world
split():     hello
split():     new
split():     world
join():  hello world hello new world --hello java 
substring():     world hello new world 
toUpperCase():   HELLO WORLD HELLO NEW WORLD 
trim():  hello world hello new world

2、StringBuffer

2.1 代码

package com.nash.java.pop.ch05_string;

/**
 * 字符串缓冲 StringBuffer
 * 1、值可变、引用可变
 */
public class StringBufferApp {

    public static void main(String[] args) {
        StringBuffer sb=new StringBuffer();
        System.out.println(sb.capacity());
        
        StringBuffer sb2=new StringBuffer("abc");
        System.out.println(sb2.capacity());
        
        StringBuffer sb3=new StringBuffer(100);
        System.out.println(sb3.capacity());
        
        StringBuffer sb4=new StringBuffer("Hello");
        System.out.println(sb4.hashCode());
        sb4.append(",");
        System.out.println(sb4.hashCode());
        sb4.append("world!\n");
        System.out.println(sb4.hashCode());
        sb4.append("welcome to ");
        System.out.println(sb4.hashCode());
        sb4.append("www.java1995.com");
        System.out.println(sb4.hashCode());
        
        System.out.println(sb4.toString());
    }
}

2.2 结果

16
19
100
356573597
356573597
356573597
356573597
356573597
Hello,world!