Java SE基础---String

测试 

public class StringDemo {
    public static void main(String[] args) {
        String s1=new String();
        System.out.println("s1:"+s1);

        char []chs={'a','b','c'};
        String s2=new String(chs);
        System.out.println("s2:"+s1);

        byte []bys={97,98,99};
        String s3=new String(bys);
        System.out.println("s3:"+s3);
        
        String s4="abc";
        System.out.println("s4:"+s4);
    }
}

运行结果

 测试

public class StringDemo {
    public static void main(String[] args) {
        char []chs={'a','b','c'};
        String s1=new String(chs);
        String s2=new String(chs);
        String s3="abc";
        String s4="abc";
        System.out.println(s1.equals(s2));
        System.out.println(s1.equals(s3));
        System.out.println(s3.equals(s4));
    }
}

运行结果 

 使用String

构造方法

 测试

public class StringBuilderDemo {
    public static void main(String[] args) {
        StringBuilder str=new StringBuilder();
        System.out.println("str:"+str);
        System.out.println("str.length:"+str.length());
        StringBuilder str1=new StringBuilder("HelloWorld");
        System.out.println("str1:"+str1);
        System.out.println("str1.length:"+str1.length());
    }
}

运行结果

 测试

public class StringBuilderDemo {
    public static void main(String[] args) {
        //public StringBuilder append（任意类型） 添加数据并返回对象本身
        StringBuilder str=new StringBuilder();
        str.append("学好java");
        str.append("月入过");
        str.append(10000);
        System.out.println("str:"+str);

        //链式编程
        StringBuilder str1=new StringBuilder();
        str1.append("Hello").append("World").append("我来了");
        System.out.println("str1"+str1);
        
        str1.reverse();
        System.out.println("str1:"+str1);
    }
}

运行结果

 String类中没有revers和append,将String转换成StringBuilder就可以使用这两个很好的方法

测试 

public class StringBuilderDemo {
    public static void main(String[] args) {
        StringBuilder sc=new StringBuilder();
        String sc1=sc.append("Java").toString();
        System.out.println(sc1);

        String sc2="Java";
        StringBuilder sc3=new StringBuilder(sc2);
        System.out.println(sc3);
    }
}

运行结果