JAVA String 类（二） 常用方法

@Test
    public void test1 (){
        String s1 = "Hello World";
        System.out.println(s1.length());
        //0-(s1.length()-1)
        System.out.println(s1.charAt(5));
        //判空
        System.out.println(s1.isEmpty());
        //转大转小
        String s2 =s1.toUpperCase(Locale.ROOT);
        String s3 =s1.toLowerCase(Locale.ROOT);
        System.out.println(s2);
        System.out.println(s3);
        //字符串匹配
        System.out.println(s2.equals(s3));
        //忽略大小写字符串匹配
        System.out.println(s2.equalsIgnoreCase(s3));

        //
        String s4 = "123"+s2.concat(s1)+s2.concat("zhou");
        System.out.println(s4);

        //比较字符串大小
        String s5 = "154";
        String s6 = "158";
        String s7 = "dadada";
        //比较的逻辑,没搞懂（涉及到字符串排序）
        System.out.println(s5.compareTo(s6));//-4
        System.out.println(s5.compareTo(s7));//-51

        //截取部分字符串
        System.out.println(s1.substring(2));
        System.out.println(s1.substring(2, 5));



    }

结果

11
 
false
HELLO WORLD
hello world
false
true
123HELLO WORLDHello WorldHELLO WORLDzhou
-4
-51
llo World
llo

代码

public void test2(){
        String s1 = "Hello World";
        boolean b1 =s1.endsWith("d");
        boolean b2 =s1.endsWith("World");
        System.out.println(b1);
        System.out.println(b2);

        boolean b3 = s1.startsWith("H");
        System.out.println(b3);
        System.out.println(s1.startsWith("h"));
        System.out.println(s1.contains("lo"));
    }

结果

public void test2(){
        String s1 = "Hello World";
        boolean b1 =s1.endsWith("d");
        boolean b2 =s1.endsWith("World");
        System.out.println(b1);
        System.out.println(b2);

        boolean b3 = s1.startsWith("H");
        System.out.println(b3);
        System.out.println(s1.startsWith("h"));
        System.out.println(s1.contains("lo"));
    }