拼接：

 public StringBuilder append(StringBuffer sb){}
 public StringBuilder append(CharSequence s) {}
 public StringBuilder append(CharSequence s, int start, int end) {}
 public StringBuilder append(char[] str){}
 public StringBuilder append(char c) {}
 public StringBuilder append(int i) {}
 public StringBuilder append(long lng) {}
 public StringBuilder append(float f){}
 public StringBuilder append(double d){}

在index位置插入：

public StringBuilder insert(int index, char[] str, int offset,
                                int len){}
public StringBuilder insert(int offset, Object obj){}
public StringBuilder insert(int offset, String str) {}
public StringBuilder insert(int offset, char[] str){}
public StringBuilder insert(int dstOffset, CharSequence s) {}
public StringBuilder insert(int dstOffset, CharSequence s,
                                int start, int end){}
public StringBuilder insert(int offset, boolean b) {}
public StringBuilder insert(int offset, char c){}
public StringBuilder insert(int offset, int i){}
public StringBuilder insert(int offset, long l){}
public StringBuilder insert(int offset, float f){}
public StringBuilder insert(int offset, double d) {}

删除 [start,end) 之间的字符：

public StringBuilder delete(int start, int end){}

删除 index 位置字符：

public StringBuilder deleteCharAt(int index) {}

替换 index 位置字符：

public void setCharAt(int index, char ch) {}

反转：

public StringBuilder reverse(){}

设置当前字符序列的长度为 newLength ：

public void setLength(int newLength){}

替换 [start,end) 范围的字符序列为 str ：

public StringBuilder replace(int start, int end, String str){}

查找字符串在字符序列中的位置：

public int indexOf(String str){}
public int indexOf(String str, int fromIndex){}
public int lastIndexOf(String str){}
public int lastIndexOf(String str, int fromIndex){}

截取子串：

public String substring(int start){}
public String substring(int start, int end){}

返回此序列中的数据的字符串表示形式：

public String toString(){}

示例：

package com.github.stringbuilder.demo1;
/**
 * @author maxiaoke.com
 * @version 1.0
 * 
 */
public class Test {
    public static void main(String[] args) {
        StringBuilder sb = new StringBuilder("helloworld");
        sb.setLength(30);
        System.out.println("sb = " + sb); // sb = helloworld                    
    }
}

示例：

package com.github.stringbuilder.demo2;
/**
 * @author maxiaoke.com
 * @version 1.0
 * 
 */
public class Test {
    public static void main(String[] args) {
        StringBuilder sb = new StringBuilder("helloworld");
        sb.reverse();
        System.out.println("sb = " + sb); // sb = dlrowolleh
    }
}

示例：

package com.github.stringbuilder.demo3;
/**
 * @author maxiaoke.com
 * @version 1.0
 * 
 */
public class Test {
    public static void main(String[] args) {
        StringBuilder s = new StringBuilder("helloworld");
        s.delete(1, 3);
        s.deleteCharAt(4);
        System.out.println(s); // hlowrld
    }
}

示例：

package com.github.stringbuilder.demo4;
/**
 * @author maxiaoke.com
 * @version 1.0
 * 
 */
public class Test {
    public static void main(String[] args) {
        StringBuilder s = new StringBuilder("helloworld");
        s.insert(5, "java");
        s.insert(5, "maxiaoke.com");
        System.out.println(s);
    }
}

示例：

package com.github.stringbuilder.demo5;
/**
 * @author maxiaoke.com
 * @version 1.0
 * 
 */
public class Test {
    public static void main(String[] args) {
        StringBuilder s = new StringBuilder();
        s.append("hello").append(true).append('a').append(12).append("maxiaoke.com");
        System.out.println(s); // hellotruea12maxiaoke.com
        System.out.println(s.length()); //15
    }
}