String 类的使用
public class StringTest {public static void main(String[] args) {//创建字符串String s = "Now";String t = s + " is the time.";String t1 = s + " " + 23.4; //运算符+会把其他类型的值转换为字符串类型t1 = String.valueOf('c'); //取得对应每个字符的字符串t1 = String.valueOf(42); //取得字符串类型的整数或一个值//t1 = object.toString();//字符串长度int len = t.length(); String sub = t.substring(4); //返回从位置4开始到结尾的字符串的子串sub = t.substring(4,6); //返回位置4和5的字符sub = t.substring(0,3); //返回位置0到2的字符//sub = t.substring(x,y); //返回位置x和y-1之间的字符 int numchars = sub.length(); char c = t.charAt(2); //取得字符串t的第三个字符wchar[] ca = t.toCharArray(); //将字符串转换为字符数组t.getChars(0, 3, ca, 1); //将字符串t的前三个字符放入ca[1]-ca[3]String caps = t.toUpperCase();//转换为大写String lower = t.toLowerCase();//转换为小写boolean b1 = t.equals("hello");boolean b2 = t.equalsIgnoreCase(caps);boolean b3 = t.startsWith("Now");boolean b4 = t.endsWith("time");int r1 = s.compareTo("Pow");int r2 = s.compareTo("Now");int r3 = s.compareTo("Mow");int r4 = s.compareToIgnoreCase("Pow");int pos = t.indexOf('i'); //第一个"i"的位置:4pos = t.indexOf('i',pos+1); //下一个"i"的位置:12pos = t.indexOf('i', pos+1); //字符串中不再有"i"，返回-1pos = t.lastIndexOf('i');//字符串中最后一个"i"的位置:12pos = t.lastIndexOf('i', pos -1);//从位置11的字符开始由后往前查找pos = t.indexOf("is"); //查找子字符串返回4pos = t.indexOf("is",pos+1);//只出现一次返回-1pos = t.lastIndexOf("the");//由后往前查找字符String noun = t.substring(pos + 4);//取出"the"之后的单词String exclaim = t.replace('.','!');//只能处理字符，不能处理子字符串String noextraspaces = t.trim();//清楚字符串开头和结尾的空格String s1 = s.intern();//返回与s相等的字符串s1String s2 = "Now";//字符串直接量会自动被保留boolean equals = (s1 == s2);//现在可以用==来比较是否相等}}?