The document contains examples of Java string and object comparisons. It shows that using '==' compares object references while '.equals()' compares object values. It also demonstrates that the Java garbage collector will call 'finalize()' on objects before removing them from memory, and that calling 'System.exit()' in 'finalize()' prevents further object creation.

1. Java small tests

2. String s1 = "Hello";
String s3 = new String("Hello");
System.out.println("s1==s3 -> " + (s1==s3));

3. String s1 = "Hello";
String s3 = new String("Hello");
System.out.println("s1==s3 -> " + (s1==s3));
s1==s3 -> false

4. String s1 = "Hello";
String s3 = new String("Hello");
System.out.println("s1.equals(s3) -> " +
s1.equals(s3));

5. String s1 = "Hello";
String s3 = new String("Hello");
System.out.println("s1.equals(s3) -> " +
s1.equals(s3));
s1.equals(s3) -> true

6. String s1 = "Hello";
String s2 = "Hello";
System.out.println("s1==s2 -> " + (s1==s2));

7. String s1 = "Hello";
String s2 = "Hello";
System.out.println("s1==s2 -> " + (s1==s2));
s1==s2 -> true

8. class Test
{
protected void finalize()
{
System.out.println("finalize!!!");
}
}
void test_finalize()
{
for(int i=0;i<5;++i)
{
Test a = new Test();
System.out.println("i = " + i);
}
System.gc();
}

9. class Test
{
protected void finalize()
{
System.out.println("finalize!!!");
}
}
void test_finalize()
{
for(int i=0;i<5;++i)
{
Test a = new Test();
System.out.println("i = " + i);
}
System.gc();
}
i = 0
i = 1
i = 2
i = 3
i = 4
finalize!!!
finalize!!!
finalize!!!
finalize!!!
finalize!!!

10. class Test
{
protected void finalize()
{
System.out.println("Exit");
System.exit(0);
}
}
void test_finalize()
{
for(int i=0;i<500000;++i)
{
Test a = new Test();
System.out.println("i = " + i);
}
System.gc();
}

11. class Test
{
protected void finalize()
{
System.out.println("Exit");
System.exit(0);
}
}
void test_finalize()
{
for(int i=0;i<500000;++i)
{
Test a = new Test();
System.out.println("i = " + i);
}
System.gc();
}
…
i = 63624
i = 63625
i = 63626
i = 63627
i = 63628
i = 63629
Exit
i = 63630
i = 63631
i = 63632
i = 63633
i = 63634
i = 63635
i = 63636
i = 63637
i = 63638