1、第一个案例

• Java语言规范要求完全相同的字符串字面量，应该包含同样的Unicode字符序列（包含同一份码点序列的常量），并且必须是指向同一个String类实例。

package string;
public class StringTest4 {
    public static void main(String[] args) {
        System.out.println();
        System.out.println("1");
        System.out.println("2");
        System.out.println("3");
        System.out.println("4");
        System.out.println("5");
        System.out.println("6");
        System.out.println("7");
        System.out.println("8");
        System.out.println("9");
        System.out.println("10");
//      如下 的字符串 “1” 到 “10” 不会再次被加载
        System.out.println("1");
        System.out.println("2");
        System.out.println("3");
        System.out.println("4");
        System.out.println("5");
        System.out.println("6");
        System.out.println("7");
        System.out.println("8");
        System.out.println("9");
        System.out.println("10");
    }
}

D:\Java\jdk-17\bin\java.exe -agentlib:jdwp=transport=dt_shmem,address=javadebug,suspend=y,server=n -javaagent:C:\Users\dgq\AppData\Local\JetBrains\IntelliJIdea2023.2\captureAgent\debugger-agent.jar -Dfile.encoding=UTF-8 -classpath "F:\IdeaProjects\JavaSenior\out\production\jdk8;D:\develop\maven\repository\junit\junit\4.13.1\junit-4.13.1.jar;D:\develop\maven\repository\org\hamcrest\hamcrest-core\1.3\hamcrest-core-1.3.jar;D:\BaiduNetdiskDownload\IntelliJ IDEA 2023.2\lib\idea_rt.jar" string.StringTest4
Connected to the target VM, address: 'javadebug', transport: 'shared memory'

1
2
3
4
5
6
7
8
9
10
1
2
3
4
5
6
7
8
9
10
Disconnected from the target VM, address: 'javadebug', transport: 'shared memory'

Process finished with exit code 0

2、第二个案例

package string;

public class Memory {
    public static void main(String[] args) {
        int i = 1;
        Object obj = new Object();
        Memory mem = new Memory();
        mem.foo(obj);
    }

    private void foo(Object param) {
        String str = param.toString();
        System.out.println(str);
    }

}
D:\Java\jdk-17\bin\java.exe "-javaagent:D:\BaiduNetdiskDownload\IntelliJ IDEA 2023.2\lib\idea_rt.jar=35590:D:\BaiduNetdiskDownload\IntelliJ IDEA 2023.2\bin" -Dfile.encoding=UTF-8 -classpath F:\IdeaProjects\JavaSenior\out\production\jdk8;D:\develop\maven\repository\junit\junit\4.13.1\junit-4.13.1.jar;D:\develop\maven\repository\org\hamcrest\hamcrest-core\1.3\hamcrest-core-1.3.jar string.Memory
java.lang.Object@404b9385

Process finished with exit code 0