What does == mean in java

In Java, the == operator is used to compare objects for equality, it checks whether two objects refer to the same memory location: Value comparison: Basic types compare values. Reference comparison: Reference types compare memory addresses. Self-reference: Two references to the same object return true. Null values: Two null values ​​return true, otherwise false.

Meaning of == in Java

In Java, the == operator is used to compare two Object equality. It checks whether the two operands point to the same memory location, i.e. whether they refer to the same object.

Detailed explanation:

• Value comparison: If the two objects are basic types (such as int, double, boolean), then == compares their values.
• Reference comparison: If two objects are reference types (such as String, Object), then == compares the memory addresses they point to.
• Self-reference: If two objects are two references to the same object, == returns true.
• null value: If both objects are null, == returns true. Otherwise, == returns false as long as one object is not null.

Example:

int a = 5;
int b = 5;
System.out.println(a == b); // 输出 true：值相等

String name1 = "John";
String name2 = "John";
System.out.println(name1 == name2); // 输出 true：引用同一对象

String name3 = new String("John");
System.out.println(name1 == name3); // 输出 false：引用不同的对象

Object obj1 = null;
Object obj2 = null;
System.out.println(obj1 == obj2); // 输出 true：都是 null

Note: The

• == operator only checks the object's memory addresses, their contents are not compared.
• To compare the actual contents of objects, you can use the equals() method.
• Avoid using == for complex objects that require comparing contents rather than memory addresses.

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