Java 常用类String类、StringBuffer类

常用类

String类、StringBuffer类

• String代表不可变的字符序列
• "xxxxxxx"为该类的对象

举例（1）

public class Test

{

    public static void main (String[] args)

    {

        //测试1

        String s1 = "hello";

        String s2 = "world";

        String s3 = "hello";

        System.out.println(s1 == s3);//true

        //测试2

        s1 = new String ("hello");

        s2 = new String ("hello");

        System.out.println(s1 == s2);//false

        System.out.println(s1.equals(s2));//true

        //测试3

        char c[] = {'s','u','n',' ','j','a','v','a'};

        String s4 = new String(c);

        String s5 = new String(c,4,4);

        System.out.println(s4); //sun java

        System.out.println(s5); //java

    }

}

• 测试1

• 测试2

• 测试3

举例（2）

public class Test

{

    public static void main (String[] args)

    {

        String s1 = "sun java";

        String s2 = "Sun Java";

        System.out.println(s1.charAt(1));//u

        System.out.println(s2.length());//8

        System.out.println(s1.indexOf("java"));//4

        System.out.println(s1.indexOf("Java"));//-1

        System.out.println(s1.equals(s2));//false

        System.out.println(s1.equalsIgnoreCaes(s2));//true

        String s = "我是程序员"；

        String sr = s.replace('我'，'你');

        System.out.println(sr);//你是程序员

    }

}

• 说明

举例（3）

public class Test

{

    public static void main (String[] args)

    {

        String s = "Welcome to Java World";

        String s1 = "   sun java   ";

        System.out.println(s.starstWith("Welcome"));//true

        System.out.println(s.endsWith("World"));//false

        String sL = s.toLowerCase();

        String sU = s.toUpperCase();

        System.out.println(sL);//welcome to java world

        System.out.println(sU);//WELCOME TO JAVA WORLD

        String subS = s.substring(11);

        System.out.println(subS);//Java World

        String sp = s1.trim();

        System.out.println(sp);//sum java

    }

}

• 说明