Top 8 Diagrams for Understanding Java

String Immutability【字符串不变性】

The following diagram shows what happens for the following code:

String s = "abcd";
s = s.concat("ef");

string-immutability

The equals() and hashCode() Contract【equals()方法、hashCode()方法的区别】

HashCode is designed to improve performance. The contract between equals() and hasCode() is that:

1. If two objects are equal, then they must have the same hash code.
2. If two objects have the same hashcode, they may or may not be equal.

   java-hashcode

Java Exception Class Hierarchy【Java异常类的层次结构】

Red colored are checked exceptions which must either be caught or declared in the method’s throws clause.

Exception-Hierarchy-Diagram

Collections Class Hierarchy【集合类的层次结构】

Note the difference between Collections and Collection.

Collections

java-collection-hierarchy

Java synchronization【Java同步】

Java synchronization mechanism can be illustrated by an analogy to a building.

Java-Monitor

Aliasing【别名】

Aliasing means there are multiple aliases to a location that can be updated, and these aliases have different types.

JavaAliasing

Stack and Heap【堆和栈】

This diagram shows where methods and objects are in run-time memory.

Java-array-in-memory

JVM Run-Time Data Areas【Java虚拟机运行时数据区域】

JVM-runtime-data-area

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