String类

string= “abcd ”
string1=”ABCD ’
string2=”learn by heart”
string3=”heart”

public class test {    public static void main(String[] args){        char chars[]={'a','b','c','d',' '};        String string=new String(chars );        //获取字符串长度        int len=string.length();        System.out.println(len);        //截取一个字符        char ch;        ch="abc".charAt(1);        System.out.println(ch);        //截取多个字符        String string2="learn by heart";        char buf[]=new char[20];        string2.getChars(9,14,buf,0);        System.out.println(buf);        //比较字符串        String string1="ABCD ";        System.out.println(string.equals(string1));        System.out.println(string.equalsIgnoreCase(string1));        //比较特点区域        String string3="heart";        System.out.println(string3.regionMatches(10,string2,0,5));        //检索        System.out.println(string.lastIndexOf("b"));        System.out.println(string.lastIndexOf("cd"));        //截取        System.out.println(string.substring(2,5));        System.out.println(string.substring(1,3));        //连接        System.out.println(string.concat(string2));        //替换        string2 = string2.replace("learn",string3);        System.out.println(string2);        //返回哈希码        System.out.println(string.hashCode());        System.out.println(string2.hashCode());        //大小写转换        System.out.println(string.toUpperCase());        System.out.println(string1.toLowerCase());        //删除开头或结尾的空格        System.out.println(string.trim());        //在字符串中插入或删改        StringBuffer str = new StringBuffer("this is a string ");        str.insert(9, " new");        System.out.println(str.toString());        str.setCharAt(0,'T');        System.out.println(str.toString());        str.append(" test");        System.out.println(str.toString());        }}