Java中String，StringBuffer，Integer，Character的属性介绍以及相互转换

public class Text1 {
	public static void main(String[] args) {

            //String:
                String s=new String("sss");
                String s1=new String("ssd");
                int begin=1;
                int end=s.length()-1;
                s.length();   //返回字符串的长度;
                s.charAt(2);  //返回索引处的字符;
                s.indexOf(s); //返回指定字符串第一次出现的位置;
                s.substring(begin, end);  //字符串的截取;
                s.getBytes();  //字符串转换成字节数组;
                s.toCharArray();  //将字符串转成字符数组;
                String.valueOf(100);   //将int类型的数据转换成字符串;
                s.toLowerCase();   //转换成小写;
                s.toUpperCase();   //转换成大写;
                s.replace("aaa", "I Love You!");  //字符或者字符串的替换;
                s.trim();   //去除字符串两边的空格;
                s.compareTo(s1);   //按照字典顺序比较两个字符串;
                String result="";
                result+="[";   //将[拼接到空字符串result后边,可以拼接int类型;

            //StringBuffer:
                StringBuffer sb=new StringBuffer();
                sb.length();   //当前字符串长度；
                sb.capacity();   //指定构造一个字符串缓冲区,返回当前容量;
                sb.append("sss");  //在sb末尾追加字符串;
                sb.insert(4,"sbsbsb");  //将字符串添加到下标为4的地方，一区元素依次后移;
                sb.delete(1,4);  //删除指定的区间的元素;
                sb.deleteCharAt(3);  //删除指定位置的字符;
                sb.reverse();  //字符串的反转;
                sb.substring(3);  //从指定位置开始截取，默认到结尾，返回新的字符串;
                sb.substring(2,5);  //截取指定区间的元素;
                sb.replace(2,5,"2222");  //将指定的区间用给定的字符串代替;
                sb.toString();  //返回字符序列的字符串表示形式;

            //Integer:
                Integer.toBinaryString(100);  //二进制组成:0和1组成;
                Integer.toOctalString(100);   //八进制组成:以0开头;
                Integer.toHexString(100);     //十六进制组成:以0x开头;
                Integer.MAX_VALUE;   //输出可以取到的最大值;
                Integer.MIN_VALUE;   //输出可以取到的最小值;
                Integer i=new Integer("3258");     //这个功能必须是数字字符串，也可以输出单个字符，但是输出的是ASCII码;

            //Character:
                //构造方法:
                Character ch=new Character('c');  //只能是一个字符;

                Character.isDigit('2');  //判断是否是数字字符;
                Character.isUpperCase('A');  //判断是否是大写字母字符;
                Character.isLowerCase('a');  //判断是否是小写字母字符;

                String s="JavaLoveYou";
                s.toUpperCase();  //将字符串所有字母转换成大写;
                s.toLowerCase();  //将字符串所有字母转换成小写;

            //String转换成StringBuffer:
                //方式1:
                String s="hello";
                StringBuffer sb=new StringBuffer(s);
                //方式2:
                StringBuffer sb=new StringBuffer();
                sb.append(s);

            //StringBuffer转换成String:
                //方式1:
                StringBuffer sb=new StringBuffer("sbsbsb");
                String s=new String(sb);
                //方式2:
                StringBuffer sb=new StringBuffer();
                String s=sb.toString();

            //将数组拼接成字符串类型:
                int[] arr= {3,2,5,8,4,7};
                //如果需要String,则就用+=进行追加;
                //如果需要StringBuffer,则用sb.append进行追加;

            //int转换成String:
                //方式1:字符串的拼接;
                int num=100;
                String s=""+sum;
                //方式2:valueOf(int i)   int-->Integer-->String;
                int num=100;
                Integer i=Integer.valueOf(num);
                String s=i.toString();
                //方式3:
                String s=Integer.toString(num);

            //String转换成int:
                //方式1:   String-->Integer-->int;
                String s="100";
                Integer i=new Integer(s);
                int num=i.intValue();
                //方式2:
                String s="111";
                int num=Integer.parseInt(s);

            //字符数组和字符串的相互转换：
                String s=new String("abcde");
                char[] ch=s.toCharArray();   //字符串转换成字符数组；
                String ss=Array.toString(ch);   //字符数组转换成字符串；

            //int类型数组转换成String类型：
                int[] arr = {24,69,80,57,13} ;
                String str = Arrays.toString(arr) ;

            //字符串转换成字节数组
                byte[] ch="hello".getBytes();
        }
}