字符串是常量,创建之后不可改变
字符串字面值存储在字符串池中,可以共享
String s = “hello”;产生一个对象,字符串池中储存;
String s = new String(”hello“);产生两个对象。堆和池各储存一个。
String name = "wangkeyue,wangkeyueiktghsd";
System.out.println(name.length());
运行结果:26
String name = "wangkeyue,wangkeyueiktghsd";
System.out.println(name.charAt(name.length()-1));
运行结果:d
String name = "wangkeyue,wangkeyueiktghsd";
System.out.println(name.contains("wang"));
System.out.println(name.contains("php"));
运行结果:
true
false
String name = "wangkeyue,wangkeyueiktghsd";
System.out.println(Arrays.toString(name.toCharArray()));
运行结果:
[w, a, n, g, k, e, y, u, e, , w, a, n, g, k, e, y, u, e, i, k, t, g, h, s, d]
String name = "wangkeyue,wangkeyueiktghsd";
System.out.println(name.indexOf("w",1));
运行结果:
10
String name = "wangkeyue,wangkeyueiktghsd";
System.out.println(name.lastIndexOf("a"));
运行结果:
11
String content = " hello world ";
System.out.println(content.trim());
运行结果:
hello world
String content = " hello world ";
System.out.println(content.toUpperCase());
System.out.println(content.toLowerCase());
运行结果:
HELLO WORLD
hello world
String content = " hello world ";
System.out.println(content.endsWith(" "));
System.out.println(content.startsWith("s"));
运行结果:
true
false
String name = "wangkeyue,wangkeyueiktghsd";
System.out.println(name.replace("a","b"));
运行结果:
wbngkeyue,wbngkeyueiktghsd
String say = "java is the best programing language,java xiang";
String[] arr = say.split("[ ,]+");
System.out.println(arr.length);
for (String s : arr) {
System.out.println(s);
}
运行结果:
8
java
is
the
best
programing
language
java
xiang
案例:
public class Test {
public static void main(String[] args) {
String str = "this is a text";
//1.将单词提取出来
String[] arr = str.split(" ");
for (String s : arr) {
System.out.println(s);
}
System.out.println("-----------------------");
//2.将text 替换为practice
String str1 = str.replace("text","practice");
System.out.println(str1);
//3.在text前面加一个easy
String str2 = str.replace("text","easy text");
System.out.println(str2);
//4.将每一个单词的首字母改为大写
for (int i = 0; i < arr.length ; i++) {
char str3 = arr[i].charAt(0);
//包装类 char => Character
char str4 = Character.toUpperCase(str3);
String str5=str4+arr[i].substring(1);
System.out.println(str5);
}
}
}
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