String类的使用及异常情况 - 黑马程序员技术交流社区

public class Demo {
public static void main(String[] args) {
String s1 = "";
String s2 = " ";
String s3 = null;
System.out.println(s1.isEmpty());//true
System.out.println(s2.isEmpty());//false
// System.out.println(s3.isEmpty());//运行时异常：NullPointerException
String s4 = "HelloWorld";
System.out.println("是否以Hello开头：" + s4.startsWith("Hello"));//true
System.out.println("是否以hello开头：" + s4.startsWith("hello"));//false
System.out.println("是否以空字符串开头：" + s4.startsWith(""));//true
System.out.println("是否以H开头：" + s4.startsWith("H"));//true
// System.out.println("是否以null开头：" + s4.startsWith(null));//空指针异常
System.out.println("是否以World结尾：" + s4.endsWith("World"));//true
System.out.println("是否以world结尾：" + s4.endsWith("world"));//false
System.out.println("是否以空字符串结尾：" + s4.endsWith(""));//true
System.out.println("------------------------------------------");
//boolean contains(string)
String s5 = "HelloWorld";
System.out.println("是否包含Hello:" + s5.contains("Hello"));//true
System.out.println("是否包含hello:" + s5.contains("hello"));//false
System.out.println("是否包含llo:" + s5.contains("llo"));//true
System.out.println("是否包含空字符串：" + s5.contains(""));//true
System.out.println("------------------------------------------");
String s6 = "jfl;sjafkdjavajfkoewutjavajfkdofewjava";
System.out.println("java第一次出现的位置：" + s6.indexOf("java"));
System.out.println("Java第一次出现的位置：" + s6.indexOf("Java"));
System.out.println("java最后一次出现的位置："+ s6.lastIndexOf("java"));
System.out.println("------------------------------------------");
String s7 = "我爱Java";
char[] chArray =s7.toCharArray();
System.out.println(chArray);//字符
System.out.println("------------------------------------------");
String s8 = "abcd";
byte[] byteArray = s8.getBytes();
System.out.println(byteArray);//地址
for(int i = 0 ;i < byteArray.length ; i++){
System.out.println(byteArray[i]);
}
}
}

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