3.1 字符串创建

3.2 字符串比较 compareTo、compareToIgnoreCase

public class StringCompareEmp{
   public static void main(String args[]){
      String str = "Hello World";
      String anotherString = "hello world";
      Object objStr = str;
      System.out.println( str.compareTo(anotherString) ); // -32
      System.out.println( str.compareToIgnoreCase(anotherString) );  //忽略大小写, 0
      System.out.println( str.compareTo(objStr.toString())); // 0
   }
}

3.3 字符串替换 replace、replaceFirst、replaceAll

public class StringReplaceEmp{
   public static void main(String args[]){
      String str="Hello World";
      System.out.println( str.replace( 'H','W' ) ); // Wello World
      System.out.println( str.replaceFirst("He", "Wa") ); // Wallo World
      System.out.println( str.replaceAll("He", "Ha") ); // Hallo World
   }
}

3.4 字符串反转 StringBuffer.reverse

String string="runoob";
String reverse = new StringBuffer(string).reverse().toString();

3.5 比较字符串区域相等 regionMatches

public class StringRegionMatch{
   public static void main(String[] args){
      String first_str = "Welcome to Microsoft";
      String second_str = "I work with microsoft";
      boolean match1 = first_str.
      regionMatches(11, second_str, 12, 9);
      boolean match2 = first_str.
      regionMatches(true, 11, second_str, 12, 9); //第一个参数 true 表示忽略大小写区别
      System.out.println("区分大小写返回值：" + match1); // false Microsoft microsoft
      System.out.println("不区分大小写返回值：" + match2); // true
   }
}

3.6 字符串格式化 format、printf

public class StringFormat {
    public static void main(String[] args){
        double e = Math.E;
        System.out.format("%f%n", e); // 2.718282
        System.out.format(Locale.CHINA  , "%-10.4f%n%n", e);  // 2.7183, 指定本地为中国（CHINA）
        System.out.printf("浮点型变量的值为 " +
                  "%f, 整型变量的值为 " +
                  " %d, 字符串变量的值为 " +
                  "is %s", floatVar, intVar, stringVar);
    }
}

3.7 字符串删除 delete

class Test{
    public static void main(String[] args){
        StringBuffer a = new StringBuffer("Runoob");
        StringBuffer b = new StringBuffer("Google");
        a.delete(1,3); // delete(x, y) 删除从字符串 x 的索引位置开始到 y-1 的位置
        a.append(b);
        System.out.println(a); // RoobGoogle
    }
}

3.8 字符串连接 concat、+

"Hello," + " runoob" + "!"; // "Hello, runoob!"
"我的名字是 ".concat("Runoob"); // 我的名字是Runoob