1、append：拼接字符串

public class UsingStringBuffer {  

    public static void main(String[] args) {
        UsingStringBuffer us = new UsingStringBuffer();
        us.testFindStr(); 
    }

    public static void testFindStr() {  
        StringBuffer sb = new StringBuffer(); 
        // 拼接字符串 append()方法 
        sb.append("This is a StringBuffer");
        sb.append("wuxp");
        System.out.println(sb);
    }
}

• 输出结果

This is a wdxp
[Finished in 0.9s]

2、indexOf：返回字符串在字符串中最先出现的位置

public class UsingStringBuffer {  

    public static void main(String[] args) {
        UsingStringBuffer us = new UsingStringBuffer();
        us.testFindStr(); 
    }

    public static void testFindStr() {  
        StringBuffer sb = new StringBuffer(); 
        sb.append("This is a StringBuffer");
        System.out.println("sb.indexOf(\"is\")=" + sb.indexOf("is")); 
        // 给indexOf方法设置参数，指定匹配的起始位置  
        System.out.println("sb.indexOf(\"is\")=" + sb.indexOf("is", 3));  
        // 返回子字符串在字符串中最后出现的位置，如果不存在，返回负数  
        System.out.println("sb.lastIndexOf(\"is\") = " + sb.lastIndexOf("is"));  
        // 给lastIndexOf方法设置参数，指定匹配的结束位置  ,从指定位置开始，从后往前
        System.out.println("sb.lastIndexOf(\"is\", 1) = " + sb.lastIndexOf("is", 1));
    }
}

• 输出结果

sb.indexOf("is")=2
sb.indexOf("is")=5
sb.lastIndexOf("is") = 5
sb.lastIndexOf("is", 1) = -1
[Finished in 0.9s]

• 注：如果不存在，返回负数(-1)

3、substring：截取字符串

public class UsingStringBuffer {  

    public static void main(String[] args) {
        UsingStringBuffer us = new UsingStringBuffer();
        us.testSubStr(); 
    }

    public static void testSubStr() {  
        StringBuffer sb = new StringBuffer();  
        sb.append("This is abStringBuffer");  
        // 从(包含)第n位截取到末尾  
        System.out.println("sb.substring(4)=" + sb.substring(4));  
        // substring方法截取字符串，可以指定截取的起始位置和终止位置  
        System.out.println("sb.substring(4,9)=" + sb.substring(4, 9));  
    }
}

• 输出结果

sb.substring(4)= is abStringBuffer
sb.substring(4,9)= is a
[Finished in 0.9s]

待续