java===java基础学习（4）---字符串操作

package testbotoo;

public class shuzhileixingzhuanhuan {
    
    public static void main(String[] args){
        
        String greeting = "hello word";
        
        //string 类的substring 方法可以实现字符串的提取，提取一个子串。
        String s = greeting.substring(3,8);
        System.out.println(s);  //结果为  lo wo
        
        //字符串的拼接
        int a = 13;
        String c = "hahhah我的";
        String d =  a +c;
        System.out.println(d);
        //不可变字符串
        
        //比如，将greeting的更改为 help!
        greeting = greeting.substring(0,3)+"p!";
        System.out.println(greeting);   //help!
        

        
        
        int n = greeting.length();
        System.out.println(n);
        int cpCount = greeting.codePointCount(0,n);
        System.out.println(cpCount);
        
        StringBuilder builder = new StringBuilder();
        builder.append("sdasada");
        builder.append(123);
        
        System.out.println(int length());
        String completedString = builder.toString();  //调用toString方法，可以得到一个string对象
        System.out.println(completedString);
    }

}